Mark decided to go show the modified portal device to his friend/classmate Nikki. He knew she ran her own portal streams fairly often and was knowledgeable about how they work. If he was to have someone assist his testing, her experience would come in handy. However Mark wasn't exactly sure what she DID with her portal receiver during streams, since Nikki always stopped the stream when someone had arrived.

He had known Nikki for years, she was one of those people that would always end up in his class every year. She was kind of a tomboy and she played volleyball a lot, most of the time she hung out with Mark like she was one of his guy friends. They'd all egg each other on to do stupid stunts, and out of the group of them Nikki told the dirtiest jokes. She liked to tease Mark a lot an push his buttons for her own personal entertainment. Sometimes she'd step on him, or use him as her replacement volleyball towel, or even catch him by surprise with a fart to the face.

It was all in good fun. Mark probably would have minded it more if puberty hadn't treated Nikki so well. She had grown two generous D-cup sized breasts and full wide hips. Nikki exercised and played volleyball constantly so her body was thin, toned and sporty. Above all else she had an amazing round ass. Occasionally she would joke around and sit on Mark's seat while he was already occupying it, calling him "her chair". Mark would laugh along and try to hide his joy, just the feeling of her big butt sitting on his legs was amazing.

There were a few moments in Mark's life where he had almost asked Nikki out. In the end his romantic feelings were pushed to the side and he decided not to ruin the good friendship that they had. That didn't matter much anymore, he has his girlfriend Megan now, but there were times where he would wonder...

He knew she would be thrilled with his invention so he left to go show it to her.

----

"You did WHAT?!" shouted Nikki, shocked and ecstatic at the same time.

Mark was sitting in her bedroom holding out the portal device for her to see. Nikki practically had stars in her eyes after Mark explained the situation. She couldn't believe he had been working with a portal production company to created a modified device.

"I said, I modified it. The company was so impressed with my work that they gave me my own device." Mark said, beaming with pride.

"And you said it can make people grow instead of shrink right? And that you could move the portals while they're active?"

"Yup!"

"Dude, with that kind of power you could almost do anything..." Nikki pressed her thumb to the bottom of her chin. She looked up at Mark giving him a serious glance. "Are you sure this isn't your evil villain backstory or something?"

There it was, Nikki's hilarious acting skills. Mark laughed off her joke.

"No no no no, nothing like that... ... or is it?" The two of them chuckled.

Nikki got up from her bed and began pacing back and forth in her bedroom. She was thinking of different ways to use the device and voicing her thoughts out loud.

"We could move the larger portal over whoever we want and shrink them! We could just portal to school instead of taking transit! You could make me into a giant! I'd be the first person to ever climb Mount Everest in a single step!"

"It'd be too cold." Mark said flatly.

"Shut up. Maybe we could charge people to use it? Nah, too risky. Can it do stuff with time? Could we travel back to the past? Could it start playing time backwards, like in reverse?"

Mark felt an odd chill. "I don't think so. I've tinkered with adding time buttons, see those blue ones there on the side? But they don't really work properly yet..."

Nikki pouted. "Maybe we could... wait, this thing can pass through any receiver right?"

"Yeah, and?"

Nikki shuddered. "I don't like the idea of that. What if someone hacks into my receiver and comes into my room without me knowing?"

"But no one else has a modified device. Just me." Mark said.

"Yeah but we don't know that for sure. I'm taking the batteries out of my receiver just in case. Someone across the globe might have made a modified device just like you. They could hack into my receiver, shrink themselves, and molest my tender body while I sleep!"

She did an overdramatic fake sob at that last part, crossing her arms over her ample chest. Obviously she wasn't as worried as her words would have him believe, but Mark could understand where she was coming from. It'd be scary to be a young girl in a world where people could just teleport inside your bedroom.

Nikki ducked down under her computer desk to find her receiver. It was somewhere between the mess of wires and cords where she had dropped it the day before. It took Mark a second to notice but when Nikki hunched down under her desk her ass stuck up in the air, pointed right at him. Her hips wiggled sexily back and forth as she absentmindedly looked for her receiver. Mark couldn't help but stare, her butt looked so good in those yoga pants.

"Got it!" she shouted, returning with the receiver. Mark nearly jumped out of his seat, pretending he was staring anywhere but at her body.

Nikki popped the batteries out of the receiver. "There, done. Okay Mark, let's start testing this thing out." she said with gusto.

Mark turned the device on. "Okay, now for the first test I think it'd be best to-" then he stopped and looked at her. She had her arm outstretched as if she was waiting for Mark to pass the device to her.

"What?"

"I want to try it out," Nikki said matter of factly. "to see if it can really hack into receivers and streams."

"No way! I made it, so obviously I'm going to use it first." Mark refused.

"Awww, come on! I'll give it right back!"

"No."

"I'll give you five dollars."

"No."

"Ten?"

"Nuh-uh."

"Twenty? Fifty?"

She was getting bothersome. Even still Mark wouldn't give in. After all the work he put into making the device he wanted to be the first one to use it.

"Nope." he said.

"Hmmmm... okay then. How about..."

Nikki hopped herself up on Mark's lap and put an arm around his shoulder. He could feel her warm skin through her leggings. He knew what she was doing. If Nikki couldn't get Mark to see things her way she would always try to use her feminine charms to convince him. Sadly for Mark, it usually worked.

"How about you let me try the device first and I'll let you touch any part of my body you want." she said, giving her cutest manipulative smile.

Mark didn't say anything. Nikki giggled.

"Come on man! I know you want to. Don't think I didn't see you checking out my ass earlier."

Mark's face turned red.

"Wha-? How did you-?" With one look at the smirk on her face her realized she was just bluffing and he had completely given himself away.

"Ha ha so you admit it! Not that I blame you, my ass is pretty sexy." she said her words confidently but Mark could've sworn he saw her blushing too. "I'll give you three minutes and you can touch my ass all you want. Or maybe you wanna touch my boobs instead? Well?"

Mark looked back at her. She was pressing her big breasts together with her arms to entice him. They looked so soft dammit. He sighed.

"...Fine."

"YEEEEEEE!! Yes!" Nikki cheered.

She leapt off Mark's lap and jumped for joy, knocking him off his chair. Mark stood back up and reluctantly handed her the portal device. While he did so, he said to her:

"You said I have three minutes to touch whatever I want right? In that case, I'm going to touch your..."

"...Ass!" Mark said.

Nikki blushed slightly at him. She must have known that Mark had been an ass man, he'd been checking out her sweet booty all the time lately. The way her tight shorts clung to it during volleyball was enough to drive him wild. He was lucky to have friend who was this hot and willing to let him do this, just so she could use his invention.

"Okay, but could you turn around for a few seconds? It's embarrassing having you watch me strip."

Mark's eye bulged "Wait, you're letting me touch it NAKED?!"

"Well yeah, isn't that what you wanted?"

"Y-Yeah!" Mark stammered back.

"Okay then turn around and close your eyes while I get ready."

He did as Nikki instructed. He could hear the sounds of her taking her clothes off. His heart beat fast, he was so excited! He was about to grope his classmate's sexy ass! Today was easily the best day ever. He had made a breakthrough in modern science and was gonna get a hot slice of Nikki's booty pie. Suddenly he heard a weird noise.

Opening his eyes he saw a human sized portal directly in front of him. He spun around to see Nikki buck naked and holding the device. As soon as he turned she began pushing him in the portal with her bare foot.

"Nikki! What the hell?!" he shouted.

"There's no way I'm gonna pass this up." she grinned as she put more weight on her foot, pushing Mark further in the portal "You'll get to be my shrunken little play toy for a while AND we'll be testing out the device. That's what you wanted right? Don't worry, you're still gonna get to touch my ass. Only, it'll be a lot... bigger."

Mark was scrambling, trying to get a grip on her carpeted floor to stop himself from falling into the portal. He should have seen this betrayal coming. Nikki loved using him as a toy to amuse herself. Of course she would try to shrink him.

Her sexy leg was strong from years of volleyball, he didn't have much of a chance against her kicking. Mark managed to catch a short glimpse of her pussy before she kicked her foot again, this time right on his face. He could smell her gross foot stench on his nose before she kicked it off him. He fell backwards into the portal, the smaller exit of which was right above the palm of her hand.

As Mark fell a short thought passed through his mind. "Well, she said I could still touch her ass. It can't be that bad right?"

Mark landed with a dull thud on the palm of Nikki's hand. Everything seemed gigantic to him, but really he was a much much smaller size. Somehow his clothes were gone too! Did she do that?

"Nikki!" he called out to her. "Where are my clothes?!"

"OKAY MARK LOOKS LIKE YOU MADE IT THROUGH THE PORTAL JUST FINE." she said in a booming voice.

Great. She couldn't hear him. He was so small that his tiny voice couldn't make more than a whisper. How small did Nikki shrink him exactly?

Before he had time to think Nikki began to move, he could feel his gut churn from being accelerated at such a dizzying speed. She crawled on her bed, stuck her nude ass up in the air, and put her head down on her pillows. In this position her butt cheeks parted naturally and she dropped him right on the line of her crack.

"I guess you really enjoyed all those times I sat on your lap with my big sexy butt, huh?" he could hear her taunting from what seemed like miles away. "Well now you're going to get all the booty you can handle, hope it's not too dirty for you."

Mark landed on her skin but this landing was a bit softer than last time. Her two ass cheeks rose above him into the sky like two high walls, insurmountable. On one side her butt crack's skin got bumpier, leading to her taint and eventually her pussy. On the other side it was smooth but leading to a giant pit. Mark felt a heaviness in the bottom of his stomach as he thought of what it could be.

Taking a short walk forward he saw it: her asshole. It was like a massive sinkhole was shaped into the earth, but made of fleshy ridges of brown skin, all meeting at a singular point. It reminded him of the sarlacc pit from Star Wars, and he shuddered to think of it swallowing him whole. There was a dull warmth emanating from it, and he could smell her pungent earthy scent lingering in the air.

Just then Mark realized how small he was. Just one of her anal wrinkles was bigger than him. It looked like her asshole could swallow multiple buildings compared to his new size. He was like a grain a sand, a spec of dust, not even tall enough to climb a penny lying flat. The monumental anus would rise and fall slightly, in pace with Nikki's breathing.

"NIKKI!!" Mark screamed. "YOU MADE ME TOO SMALL!"

Nikki couldn't hear his voice, it was too quiet and too far away. She hadn't checked his size before dropping him on her ass either, she just assumed he came out the portal an inch or two tall. It wasn't even one out of her three minutes that she was keeping him down there and she was already bored. What does she do?

"Hmm, just lying here is kind of boring... isn't there anything else this thing can do?" Nikki said, as she started to play with the portal device.

She was flipping it this way and that in her hands, turning it all around to find something to mess with. Maybe there was a way to make Mark vibrate uncontrollably? Nah, that probably wouldn't be a feature Mark had in mind while making this thing. She poked at it in multiple places and pressed the blue "time" buttons Mark mentioned earlier but nothing happened.

Rather, nothing happened to her. On Mark's end he could feel the effects of the buttons he thought to be defunct. A loud voice shot through his head warning him like a siren.

"TIME STOP: ON. TIME STOP: OFF. TIME FAST FORWARD: ON. TIME FAST FORWARD: OFF. TIME SLOW DOWN: ON."

What? Great. Nikki had absentmindedly put him into slow motion. Not only that, but since he was the only one who went through the portal, he was the only person who heard the warning. Everything from his perspective was slowed down, Nikki's actions, his own movements, they all slowed to a crawl. His short, three-minute visit to her asshole just got a lot longer. At least things couldn't get worse right?

Finding nothing good from the device Nikki thought of what she could do next to mess with Mark. She wiggled her big butt around, hoping she could feel Mark rolling around in her crack. She couldn't sense him though, he was around a hundred times smaller than she thought he was, and her dainty hip gyrations were akin to a horrific earthquake. Nikki pouted with dissatisfaction, but then felt her intestines churn from wiggling her ass around. She couldn't feel Mark or hear his tiny yells of protest from her ass but maybe giving him a little gassy present would upset him enough.

She pressed a hand to her abdomen, she could feel her past meals floating around inside. Giving it a little push, she sent more and more intestinal air Mark's way. It reminded her of how she would always fart in his face when he least expected it, only on a much bigger scale. Sometimes Nikki couldn't help herself from messing with Mark, his reactions were always so entertaining. It's not like she disliked the guy, toying with him just felt so good. When he first came to her house and told her that he made a portal device, Nikki thought about shrinking him down and she had been saving up her farts ever since.

When Nikki was wiggling her ass around it had knocked Mark off his feet and he tumbled down the bumpy sinkhole that was her anus. He rolled all the way until he was nearly at the center of her massive orifice. Accidentally, he wedged his legs between the tight wrinkled folds of her smelly skin.

"Oh shit!" he yelled, his words coming out slowly.

Nikki's backdoor had effortlessly trapped him in its grasp. He pushed against the dark skin to heave himself out but it was no use, he couldn't budge. A storm was brewing underneath Mark as Nikki's bowels began to fill with gas. Her anal muscle instinctively clenched, if only a small amount. It was a slight twitch of her anus, but to Mark it was a huge event.

The ring of wrinkles pulled back inside Nikki a little bit, dropping him downwards what felt like several stories. The asshole closed up and shrank as it descended, its compressing folds steamrolled over Mark. He was crushed on all sides by Nikki's anal bands, her body's involuntary movements had wedged him so far up her asshole that he was no longer visible to the outside world. The tight heavy wrinkles overhead had closed to the point that they blocked out all light and Mark was left in the suffocating dark.

Nikki's ass felt full. Her fermented gases had filled her bowels to the brim and they were pressing right up against her tightly shut sphincter. She giggled to herself, it felt like it was going to be a big one. She thought of Mark, laying right on her asshole, with no idea that she was about to blast him. After letting her gas build and build all day she was really going to let him have it.

She relaxed her anal muscles and felt her butthole pucker, ready to burst. Nikki grunted and pushed slightly, causing her anus to explode with a huge fart. It was loud and long, creating a droning rambunctious sound as it filled the room with her foul feminine odor. Nikki closed her eyes as she felt the huge bubble of gas inside her pass through her exit hole. She savoured the feeling. The strong bubbly fart lasted for almost ten seconds before it was over.

That time for Mark was like hell, but even worse. The claustrophobic space of her tight asshole was starting to run out of air. He wriggled, squirming to get himself free, but her planet-sized ass didn't give. After several minutes (to Mark) the anal maw clamping down on him began to relax. First the grip loosened and then the whole hole spread apart, allowing him to breath her stinky aroma once more in full. It was better than nothing. Then the anus lifted back up, returning to its original position.

Only it didn't stop there. The anus kept rising and rising as the gas inside knocked on its door. Mark felt like he was on top of a growing mountain, and heard an ominous groaning from within. The tight wrinkles expanded and grew puffy, releasing Mark from its clutches. Then it puckered. The gigantic anus bulged outward, revealing the pink center inside. It flowered open at Mark's feet and he slipped and fell down on it. The surface of the pink puckered anus was hot and felt more like raw meat than skin. As it slowly grew more and more open Mark felt the trembling flesh with his hands. It was sticky to the touch, from her internal juices. He lifted his hands back up and ropes of awful smelling slime fell from his palms.

"Oh God..." he shuddered. It was around then when Mark pieced together what was about to happen. NIKKI WAS GOING TO FART-

He opened his mouth to scream but it was too late. A small gap opened from Nikki's anus and a jet of gas shot through it in slow motion. The ground rumbled and shook before breaking apart. Her giant anal wrinkles spread apart allowing the teenage girl's enormous fart to rush outwards. The booming release flipped him through the air, Mark thrashed as he was engulfed in Nikki's heavy stench. Her fart was so huge, so amazingly gigantic that he got lost in it. It was as humid and muggy like being inside a sauna that smelled awful. It gave Mark flashbacks to when Nikki would tease him by farting in his face only a thousand times worse.

Nikki continued to rip ass as Mark flipped through the air in slow-mo. The brutal blast knocked him aside, to the rim of Nikki's shithole. Mark stuck to the side of it, sticky with anal juices and with the force of her fart to press him against it. Her asshole was a terrible place to be in right now, even in slow motion her anal wrinkles were rapidly flapping in the wind. He was forcibly wedged between two puffy wrinkles as they vibrated back and forth pounding him on either side. The wind was completely knocked out of him and all he had to breathe was Nikki's rancid gas.

It was like being in the center of an explosion. His tiny micro-sized body stayed wedged in Nikki's hot folds while her enormous fart roared and howled. To her it was a fleeting moment, a short burst from her butt for some intestinal relief, but to Mark it was unending torture. He screamed and yelled for anything to save him but Nikki's ass continued to carelessly exhale her hot smelly gas. The dirty anus undulated violently around him, smacking him over and over with its flapping wrinkles. They were warm and disgusting and the way they moved in slow motion seem unnatural. He could see the blazing hot air in the light distort around him. It was like he could actually see her fart as it slowly expelled from her ass.

When Mark woke up this morning his first thought wasn't anything like "I wonder how Nikki's anus looks up close when it farts" and yet somehow he now had that answer. Thanks to his poor decision making and her disregard for his well-being he had ended up inside her farting butthole. After what seemed like forever her gas had started to trail off, saving Mark the hottest thickest flatulence for last. He cringed as he breathed in the burning air, his lungs seared with pain. But once that last bout of her fart finished Nikki was done, and her anus began to close back up again.

The puffy pink flesh closed around Mark completely burying him in her anal flesh. Crammed inside the wet folds of Nikki's inner anus, Mark was helpless as the smellhole shrank back up and pulled him inside like nothing had ever happened.

"NOOOOOOOOOOOOOOOOOOO!!!" He screamed.

It was like when the anus had clenched on him before, only this time he was even deeper inside her. The walls made a deep wet squelching sound as they squeezed his body, still red-hot from the recent fart. The remaining air was ten times worse too, he chocked on her strong potent stench. He had survived a giant-sized fart, but now he was scared to death that he was about to be swallowed completely inside his classmates bowels.

"Mmmmmn... that felt good."

Nikki smiled after her fart. Letting out that much gas was a big relief, and knowing her little friend was getting the tail end of it made her feel satisfaction. To her it was a very pleasurable experience. This whole idea of shrinking Mark and making him her ass toy was pretty good. Maybe she wasn't ready to let him go just yet...

Nikki made up her mind for what she was going to do next and decidedly slapped her ass. She smiled as her big round butt wobbled around. Knowing that her tiny friend was taking the brunt of her butt amused her. She knew he was down there, probably coughing on her recent gassy release, but what she didn't know was she shrunk him too much, to a nearly microscopic size. She picked the portal device back up, taking it off the bed and accidentally pressing a few more buttons on the side.

"TIME SLOW DOWN: OFF"

Mark felt his stomach lurch signifying his return to a normal speed of time. Things weren't going in slow motion anymore, not that he could really tell a difference from his surroundings. He was thoroughly lodged within the folds of his mischievous friend's anus, shrunken down to a size where he was powerless to fight back against her grasp. Just then he heard Nikki's voice, muffled from inside her butt, but still booming loudly up above.

"This portal device is amazing Mark! I'm surprised it works so well. You're so small I can barely feel you in my ass crack! Or maybe that's just because my butt's so big, hee hee" she laughed.

"NO NIKKI! YOU MADE ME TOO SMALL! GET ME OUT OF HERE NOW!" Mark screamed, his faint voice not even traveling outside her ass.

"I'm going to do you a little favour, okay Mark? I know initially I said I'd only allow you to touch my ass for three minutes, but I'm soooo impressed that I think I'll extend your time for the rest of the day. We both know it's what you really want, it's what you chose remember?"

Mark's heart sank. She knew he was trapped in her ass but she was going to keep him there all day? Even if he wasn't micro-sized this would be too cruel.

"I've still got a few more classes left in the day, so I'll be heading to school alright? You have fun down there, but don't enjoy yourself too much." she said playfully as she got dressed again.

This time instead of wearing her sexy yoga pants she opted for just her panties and a skirt. Nothing would be better to tease Mark with than seeing his freedom, just a small layer of fabric away. He'd be stuck in her panties until she decided to let him out, left to face her humongous butt cheeks and unbearable weight as she sat on him (and maybe a few farts too). The times where she used to sit on his face to tease him were funny because she could feel him squirm under her ass. Today was bound to be even more enjoyable because her ass was so much bigger and he was so much smaller than her.

She could hardly contain her laughter as she walked to school. Her big fat butt wobbled around in her panties as she walked, surely crushing the tiny boy. Nikki's ass was bigger than most girls and the sheer size of it made her cheeks jiggle with every step. The way her huge pale cheeks slid against each other admittedly felt good and she hoped Mark was rolling around in deep the crack between them.

Mark wasn't dealing with the tumbling glory of Nikki's ass cheeks, but honestly he'd rather be there than where he currently was. The tight anus was cramped and smelled awful, with blazing heat to match an active sauna. Every breath Mark took smelled like leftover farts, it almost made him sick. It smelled so bad in her ass, if the anus swallowed him fully he didn't know what other horrors would lie within. He had to get out of here before that happened.

Only he was stuck. The stained hole had a firm grip on his body and worse yet, it seemed to grind him left to right his giant friend walked to school. He was wet, both from traces of Nikki's ass sweat and his own. Maybe he could use that to his advantage and slip out? No good, it wasn't enough lubrication to actually let him slide around.

One of his arms however, felt a different kind of wetness, stuck between two wrinkles of Nikki's asshole. Scooping it up in his hand he discovered it wasn't shit, but rather mucus-like slime, the kind that would normally coat the bowels to ease feces through the lower intestine. It seemed like Nikki had an overabundance of anal juices in her ass, and for the first time it looked like Mark had a stroke of luck.

He slathered the goopy slime all over his body. It was warm, and smelled absolutely horrible, but he had to deal with it if he wanted to escape. He coated himself until he could roll around in the sticky gunk, he was finally slippery enough to take action. Slowly he began to slide himself backwards, out of the massive anus. The lumpy pucker squeezed down on him, almost like it wanted him to stay inside, but the overbearing flesh only served to push him out more, aiding to his escape. Before long, Mark could feel fresh air on his legs, then his torso, and eventually his head.

The tiny boy didn't know what he was in for. Finally free of the teen girl's nasty asshole he found himself in a world bigger than he could have imagined. He hadn't experienced Nikki's plump ass cheeks in full yet. Sure he had seen their hills rise above him when she dropped him in her crack, but he hadn't experienced how it felt to be smushed between them. The continental weight and girth of her buttocks instantly overwhelmed his micro body, sucking him into a constantly-moving tornado of flesh.

The girl marched on, her huge white globular butt cheeks pulverized the tiny man between them. Mark screamed as he endured the wiggling booty, stuck in an unending ocean of salty skin. He couldn't tell where it stopped or where it ended, what way was up or what way was down. All he knew was that the trek to school was a lengthy one, and Nikki's butt would smother him the entire way. Her massive chubby buns pumped up and down in rhythm with her thick thighs. Mark belonged to her meaty crevice now, and for the many excruciating minutes to come...

Later Nikki arrived at school, in time for afternoon math class. She made her way to her seat and sat down as slowly as possible without garnering anyone's suspicion. Her butt slowly stuck out from within her short skirt, the massive cheeks spreading apart ever so gradually. She wanted Mark to fall to the bottom of her panties, so he would be crushed between the hard surface of her chair and her giant fat rump.

Mark did indeed fall to the bottom of her underwear, landing on the soft stitched fabric. Looking up he saw a daunting sight, Nikki's full spread ass, bent over and hovering above him. The monolithic globes took up the whole sky, dimly lit by the small beams of light that passed through her panties. It was so huge, so astronomically big that Mark couldn't see it all at once. Her ass extended infinitely far into the horizon, it was the size of a small town and gave Mark perspective as to how small and insignificant he truly was.

Nikki's hands quickly grabbed onto her buns and spread them apart as she sat. Mark's jaw dropped in reaction. She wanted to sit on him with her ass spread, so he'd be flattened under her filthy ass crack and anus.

"Holy shit..." were the only words Mark could meekly utter as the sky fell down and sat on him.

With a heavy creak, Nikki's fat ass was seated and ready for class. She was in a good mood today, it wasn't often she got to torture Mark like this, and only using her butt. As expected, Mark was pinned against the girl's puffy backdoor again, stuck between it and the hard unforgiving seat. This was going to be a long day.

As class went on Nikki shifted her huge ass around in her chair. She was trying to smear her gross anus all over Mark, still under the assumption that he was an inch tall and that she was just playing around with him. In reality however, Mark was much much smaller to the point where just one of the wrinkles of her anus dwarfed him in size. Nikki only wiggled her ass around slightly, as not to draw attention to herself, but her small movements were akin to a world-shifting event from Mark's perspective. The gigantic stuffy anus dragged him from side to side, steamrolling his tiny powerless body. None of his weak screams were loud enough to penetrate the thick barrier that was Nikki's seated buns.

Even by normal-sized people's standards Nikki's teenage ass was huge. Her plump booty and thighs were big enough to spill over the sides of her school chair. She bit her lip imagining Mark being swallowed up and helpless inside her crack. Using her big butt to dominate her friend felt so good, it excited her that she was doing this in the middle of class.

Meanwhile Mark was fighting a losing battle with her anus. The oily pucker was pummeling him into the back of Nikki's panties, right up against the hard surface of her chair. Her disgusting wrinkles tumbled over top of his body, each time threatening to pinch down on one of his limbs. Mark was terrified at the possibility of her anus grabbing hold of him, he was certain that if it did it would completely gobble him whole. As time went on he could feel Nikki's muscles clench and her anus folds contract on him a few times. She was clearly enjoying this feeling. Mark shouted in pain and frustration. Just knowing that she was getting off on smothering him in her ass was awful, especially when she had no idea of how much danger he was really in.

She couldn't even pay attention to the lesson, this was just too much fun. It was decided then that today would be dedicated to playing with Mark in her ass. As she daydreamed of what she could do next with her rump, her stomach growled. That gave Nikki an idea, her lips curled into a mischievous smile.

Mark heard a distant ominous rumbling sound. Suddenly her ass stopped moving. A bright light then blinded him temporarily as one of her tremendous ass cheeks lifted skywards. The light was flooding in from the outside world, through her panties. At first he thought she was getting up from her seat and his torture was over but then his heart sank as he realized she was just lifting one leg. If she wasn't getting up it could only mean one thing: She was about to blast him with a fart.

Mark ran as fast as he could, making little ground in the vast expanse of her panties. The fat meaty buns towered above him, like a slanted ceiling as high as the clouds. He couldn't go far, the underwear eventually curved upwards with the ass, forming a impassible net of cloth. He gripped the strands of fabric walling him inside, the criss-crossed weave looked like prison bars to him. Outside he could see the person sitting next to Nikki, his friend Allyson. He yelled as loud as he possibly could to get her attention but it was no use. There was no way she ever could have heard him, he was just too small.

Falling to his knees, Mark felt hopeless. There was no way out. He turned around to see Nikki's anus peeking out behind her cheeks. It grew larger and was puckering, just about ready to fire.

"Nikki.... Noooo..." Mark sobbed.

Her ass let out a short sharp fart with big squelching noise. It was a wet one. A big gob of her anal slime shot out from her asshole, landing on top of Mark with a splat. He had no way to avoid it, it was bigger than a house. For a moment he panicked, wondering what the hell had just happened. He was encased in the middle of the juicy gob and stuck to the bottom of Nikki's panties. He couldn't even see through the slime, it was too murky with brownish traces of her anal filth. The whole thing smelled horrible and clogged up not just his nose, but every crevice of his body. Completely encased in the glob Mark had nowhere to move and nothing to breathe.

Nikki's eyes widened when she felt how wet her panties had just become. She went too far. She was expecting a hot silent but deadly fart, not a wet sloppy one. Worst of all the whole class heard it and turned to look at her. Her face grew red with embarrassment and she timidly sat her ass back down in the chair. Mark felt the world go dark as her ass came crashing down on top of him again. Her butt shifted and the gob of wet sticky juices was wedged right between her two cheeks.

Mark remembered how Nikki's anus had an overabundance of slime inside it and how he used that to escape. Her rectum must have been backed up with tons of sticky juices and her fart must have blasted some of them out. The tiny boy tried to escape only to realize the cold hard reality: he couldn't move an inch. With all the strength in his muscles he couldn't get his arms or legs to go. The sticky mucus was just too thick. His body craved for him to breathe some air but he was encased in nothing but gross anal slime. He struggled what little he could, trapped in the sticky pool at the bottom of Nikki's panties, with her huge fat ass seated on top of him.

He didn't want to die here, but with every passing second it seemed like he was doomed to. It awful, getting killed by the disgusting gunk that lined the walls of a girl's ass tunnel. Her hot anal juices that would normally ease her shits along were being used to end a life, unaware to their owner. Mark would have rather been crushed or gassed to death than this, it was just too scary and pitiful. Nikki has no idea that under her butt her friend was struggling desperately or his last breath, she had gone back to doing her work.

Mark's lungs burned for air, instincts fighting over his common sense not to breathe. He tried to get a small bubble, any pocket of air he could find inside the frothy mixture, but all he got was a mouthful of slime pouring into his lungs. The hot gooey juices burned his mouth with the taste of her shit, causing his heart rate to accelerate. He began to drown in her slime, his mind screaming for Nikki to save him. Her finger, another fart, anything to get him out of this shit-stained gob of death. Mark twitched and choked on her mucus slowly watching his whole world go dark...

Nikki checked her panties after class, disposing of the gob in a tissue and flushing it down the toilet. It puzzled her to the whereabouts of her friend until she realized she hadn't actually seen him since she put him in her ass back in her bedroom. He must have escaped there, right? She put her panties back on and returned to classes, determined to find Mark in her room when she came home. She never did.

Nikki smiled to herself. She couldn't feel Mark's presence trapped inside her panties, but in her mind she knew he was down there. Sitting on a shrunken boy toy in class was pretty exciting, and thoughts started to fill her head of how she could tease her little friend. She could start by rubbing her ass into the hard seat, rolling her juicy butt cheeks over him. He was already so far up her crack that just by leaning back she could smother him with her sweaty asshole. Maybe she could even sneak a little fart on him...? Her brainstorming came to an abrupt end when the teacher called on her.

"Nikki!"

"Y-yes?!" she stammered, being brought back from her fantasies.

"You better not be looking at your phone over there again! Today's class is important! If you don't pay attention you're not going to pass the test next week!"

"Okay! jeez..." she replied, that last part under her breath.

Reluctantly Nikki opened up her textbook and followed along with the lesson. Seems like she wasn't going to any have fun teasing her tiny friend this period after all. She needed to concentrate on the lesson and ignore the little passenger in her panties. Oh well, Mark was so far up her massive butt crack that his 1-inch body wasn't going anywhere.

----

While Nikki was right about him not going anywhere, she was still wrong about one thing: Mark was not 1-inch tall. Due to her earlier mistake Mark was shrunken down to a near-microscopic size, about as big as a grain of sand.

"How could she not have noticed something is wrong by now?!" Mark thought to himself, frustrated. "She dropped me in her ass, farted on me, walked all the way to class, and sat down on me without even checking if I was the right size! Is she stupid or something? Does she not care?"

For the moment, no. She was too busy trying to copy down notes to even think about Mark's situation. If she didn't pass the upcoming test her grades would be in a dangerous spot. Not quite as dangerous as where her little friend was, pinned to the chair by her booty hole. Even something as small as her anus still dwarfed the boy in size. Its puffy wrinkles pressed into his body, wedging him snugly between them. He counted himself lucky she wasn't sweating right now. If a single droplet of sweat happened to roll down her ass crack it could drown him underneath her pink hole. For now he had no choice but to wait inside Nikki's cramped humid crevice, while she focused on the class up above.

Leaning forward into her notes, Nikki's butthole slowly raised upwards, off the chair. Mark finally felt freedom from her gross pucker, or at least he would have if it hadn't snagged him by the arm and lifted him upwards too. His arm was clamped inbetween the folds of her anus like it was in a vice, and the rest of him was partially stuck to her with the help of the sticky oils that lined her skin. It was so dank and slimy next to her asshole that he stuck to it like fly paper, trapped while his arm was crushed.

Nikki's asshole was motionless, giant and unfeeling towards Mark's struggles. It felt like it was so active before, but now it was completely still. He could scream and pound on it as hard as he could, it wouldn't even flinch. Not that he had a chance to fight back, when Nikki leaned forward in her seat something else began to happen.

Her panties, deftly hugging the curves of her butt, shifted slightly. As she moved her hips forward, Nikki's round posterior pulled on the fabric. Also, thanks to her playfully spreading her cheeks before sitting on Mark, the underwear rode all the way up her ass. It invaded the depths of her crack, just stopping dead in front of the dirty hole. Completely by chance, a small, insignificant piece of lint got pulled up with the girls panties, and was lightly touching her backdoor. Even as tiny as the piece of lint was, it was still the size of a house compared to Mark. His strongest punches couldn't do anything against the colossal asshole, but the lint was able to faintly tickle it. Mark felt rumbles give way as the anus began to stir.

"Oh fuck! It's tickling her!" Mark yelled in panic.

In reaction to the lint Nikki's asshole started to spring back to life. On reflex it began to contract to try and get rid of the tickling sensation. Puffy flesh engulfed Marks whole body, pulling him inwards with the other huge anal wrinkles. He was smothered on every side by sticky lumps of skin until the anus unclenched and expanded back outwards. Mark tried to pull himself free, but now both his arm and his leg on one side were trapped inside the anus. Still being itched by the piece of lint, the giant hole contracted again, sucking Mark further inside. He desperately struggled against the pulling force, hurriedly digging through mounds of sphincter meat in a race to stop himself from being sucked inside. As hard as he tried it was a race he was slowly losing.

Meanwhile Nikki was still absorbed in class, with no idea what was going on in her bottom. The small piece of lint itching her body didn't even register in her mind, her ass was acting completely on reflex. She was calmly scribbling notes on her paper while her friend was fighting a life or death battle with her big fat ass. It was going to devour him whole, slowly chew him up and swallow him, without its owner even realizing. She was just sitting there, having completely forgotten about Mark for the time being. He was about to be eaten alive and had no possible way to get her to hear his screams.

"Nikkiiiii!!!" he shouted. "Your asshole! Stop your asshole- I'm too small! It's swallowing meee-MMMPPHHUURRGH!!!"

The uncaring anus clenched again on Mark, still trying to get rid of that pesky itch. With every flex he was sinking more and more into her asshole until he was no longer visible to the outside world. Oily walls surrounded him on all sides, pulling him deeper into the darkness. It smelled awful in there, the flesh was stained with the stinky remnants of past meals. Mark tried to not gag at the stench, even though he knew it would only get worse as time went on. The lint wouldn't go away, it continued brushing across the pulsating folds of Nikki's anus, encouraging it to keep contracting.

Mark had just barely escaped the metaphorical jaws of Nikki's asshole from swallowing him before, but this time it looked like he was fucked. The slime, the thick mucus-like anal juices that had once helped him pull himself out of Nikki's anus were now having the opposite effect. Instead of being lubricated enough to pull himself out, now he was lubricated enough to help the asshole pull himself in. The girls heavy turd-cutter would squeeze down on his body and hot gushes of slime would slather him from head to toe. The deeper he went the more rancid it got, the smell was so intense it felt like it was physically burning him. Or it could be the blazing heat of Nikki's inner ass, either one. Worse yet, in trying to breathe Mark got some of the disgusting slime in his mouth and was forced to taste her shitty juices.

The sticky anal mouth continued its consumption Mark's helpless body, all without its owner knowing. Every clench was excruciating, but these were only light twitches in response to a tickle. If Nikki was clenching her asshole on purpose Mark's body would be popped like a grape. He was nothing, a mere speck compared to the glory of Nikki's gigantic ass. None of it mattered anymore. He would have given all of his possessions, even the modified portal device in exchange for her to blast him out with a fart right now. Anything to stop him from being sucked all the way inside her bowels.

But nothing happened. Mark felt his legs enter a spacious room, followed by the rest of his body as he slumped through the other end of Nikki's hole. The air was sweltering hot, like a sauna, and the smell was a hundred times worse than the outside. Mark fell to his knees and wretched on the surface of the fleshy bowels. Back on the outside the piece of lint finally loosened and fell down the giantesses panties. The massive shithole gave a few more pumps until it couldn't feel any more disturbances and then stopped moving altogether. It was too late for Mark now. He was already past the wrinkled gate and burning inside hell. He was trapped inside the ass of his unaware friend and she had no way of knowing he was in there.

The hot steamy bowels of Mark's friend was like being inside another world. The atmosphere was heavy with the thick smell of female gases. It permeated through the entire area, slowly choking Mark. He felt like he had been transported to another planet without a space suit. Only it wasn't another planet, it was his friend Nikki's ass. Her hungry butt had swallowed him whole without her even realizing. She still thought he was trapped in her panties at an inch-tall, not the size of a grain of sand stuck inside her poop chute. Mark was at least thankful to not be crushed by her grueling anus, but now that he was on the other side of it he had to deal with a whole new world of problems.

Besides the overbearing stench wafting from within, he realized he was totally blind in the dark, and waist deep in anal slime. The natural substance was for easing shits along Nikki's bowels, but Mark noticed that she had an overabundance of it. Beyond where he was standing stretched out a long lake of ass juice, coating the nooks and crannies of her lumpy anal walls. It drooled from the ceiling like melted butter, dripping into the pools below. He had no idea what she ate for her bowels to get like this, but there was so much ass juice it was ridiculous! This wasn't a normal thing! He wouldn't be able to stand up anywhere in the tunnel, the volume of gross ass-mucus went well above his head.

Low groans echoed from deep within Nikki's body. The chamber contorted slightly, sloshing the juices around. Waves of sticky slime lapped against the back of her asshole where Mark was standing, threatening to pull him under. He needed to get out of here. If he ended up in that viscous pool he didn't know how long he could last. Plus with due time something was going to pass through the tunnel and crush him.

He turned around facing her anus and tried to push his way through. The muscle was shut impossibly tight, without even a gap to crawl in. Taking two wrinkles between his arms he tried to force them apart but it was no use. He might as well have been trying to push apart two mountains. He slammed the rubbery asshole with his fists to no effect. The anus just stood there, like an unmoving giant. His only door to freedom. His only chance at survival... and it was closed off to him. Mark fell to his knees in despair. Was it hopeless? What he didn't know was, it was about to get a whole lot worse.

----

Nikki was still at her desk, following along with the teacher's lesson. She needed to get as many notes written down as possible for the upcoming test next week. Suddenly a cell phone rang. She perked her head up to see whose it was, and surprisingly it was the teacher's.

"Hmm? Yeah. ... Damn, I need to take this. Everyone gets start on today's homework until I get back! It's on the board!" he instructed, quickly exiting the classroom.

"What the hell? He gets to use his phone whenever he want but yells at me?! I wasn't even using my phone that last time! Hypocrite..." Nikki thought angrily.

Looking up at the clock she saw it was nearly the end of class. Soon she could get back to toying with her little shrunken buddy... Come to think of it, Mark had been awfully quiet throughout the whole class. In fact, she hadn't actually felt him at all since she shrunk him down and dropped him in her ass. He should have been squirming around down there trying to fight back against her huge butt. She had known Mark for a very long time, he wasn't the type to take this sort of thing lying down. So why didn't she feel him?

Nikki tried clenching her asshole to see if she could detect Mark. She squeezed her anal ring trying to feel him out. If he touched her sensitive pucker she'd know, and if it clamped down on his arm or something she would be able to feel it. Yet oddly enough she didn't feel him lodged up her butt crack. She relaxed her muscles and waited, maybe for a little wriggling feeling by her backdoor but nothing came.

"Hmmm, that's weird..."

She kept squeezing with her ass, over and over, trying to feel his body. Her butthole tightened and relaxed repeatedly, earnestly pulsating inside her panties. Nikki sat there puzzled as she flexed her inner ass muscles. Mark should be yelling and flailing for mercy by now, so where was he? Did he fall out of her panties? Was he too small to feel? She started to think about it, wondering exactly how small she shrunk him in her room, all the while contracting her huge booty again and again and again...

----

When Nikki first clenched her asshole it gave Mark much more than just a surprise. He had been on his knees, lamenting ever showing Nikki the portal device in the first place, when it happened. The backside of her anus twitched suddenly, shortly followed by the entirely of her anal cavity caving in. Mark didn't even have time to scream before the walls scrunched up and a massive tidal wave of juices hit him. His micro-sized body was swept away in the mass of goop, carried far away from the only exit. Nikki's colon walls quivered as she squeezed with her butt. She didn't have a clue that in trying to locate her tiny friend she was making him more lost than ever.

Deep in the ocean of slime, Mark found himself to be powerless. The mixture of bodily fluids was like molasses, entirely too thick for him to swim through. He could only drift and wait for his air to run out before he drowned. After a few seconds however the walls stopped clenching. The runny juices drained to the floor of the anal tunnel again, slowly sliding off the sides as it expanded. Mark found himself lucky for once. His body happened to stick to the side of Nikki's colon, free from the pooling liquid below. With his back stuck to the fleshy wall, he used his free arm to wipe his mouth. He scraped a layer of slimy film away from his face tried to gasp for air, but before he could the ass began clenching again.

Mark got an extra large helping of anal juices in his mouth, the disgusting taste adding to his torture. The puffy walls plunged him into the wetness again, tensing up as they did so. From all sides the boy's anal prison was compressed until no air remained. There was only slime and hot throbbing muscle. It wasn't long before the bowels relaxed again, only to squeeze down once more without missing a beat. The mighty ass started to clench rhythmically, tossing Mark into a juicy, fleshy nightmare. His shrunken body was thrown all over the place. Sometimes he was dripping off the ceiling, other times he was pounded at the bottom of a lake of slime. He got in gulps of air where he could between the clenches, but he didn't know how long he could keep this up.

Nikki's godlike butt didn't hold back either. It kept chewing Mark up like it was a giant mouth, drooling from every surface. Pulsating and squeezing continuously, the ass tunnel swished his body around in a whirlpool of slime. Waves of it splashed across the walls as they munched down, creating a frothy cocktail of fart juice. Sickening SQUELCH sounds filled the chamber, echoing off the undulating intestine. It was all Mark could hear. Every single one of his orifices was filled with Nikki's juices and each time the ass clamped down he felt the tremendous pressure push the slime deeper inside his body.

One especially cruel clench pinned him between two thick lumps of collapsing muscle, squeezing all the air that he had saved up in his lungs. Mark's pained screams came out as bubbles in the thick goo, and joined the rest of the bubbles in the frothy storm. With loud wet chewing noises the ass canal continued to pump inwards and outwards, ignorant to Mark's lungs burning from lack of oxygen. He broke the surface of the heavy juice pool only to be hammered back down before he could have a chance to breathe. He was being drowned in possibly the worst way imaginable, deep inside his friends ass as it throbbed him to death.

Nikki was starting to worry. Maybe she actually couldn't feel Mark in her panties because he was too small. Quickly digging into her school bag Nikki looked at the portal device's last settings. Time slow down? Either way, when she saw the size she shrunk Mark down to her heart sank. She wasn't sure how small he was, but a decimal point with that many zeroes after it couldn't be good.

The bell rang and Nikki shot up from her seat. Charging her way through the crowd, she made a mad dash to the nearest ladies washroom. She needed to check if Mark was safe! Nikki slammed the stall door closed and pulled down her underwear for a panty check. Her huge bare ass sank into the toilet seat as she examined the panties, bringing them as close to her face as possible. She gulped nervously. There was no sign of Mark.

Was he stuck in her ass crack? Or even deeper? Without a mirror Nikki had no way of checking her plump behind, and if she waited until she got home Mark could already be dead! As Nikki panicked, her insides began to churn. Her ass, feeling the familiar touch of the toilet seat, started to growl. Nikki felt a fart coming on, and got an idea. As gross as it was, if Mark was stuck up her booty, maybe she could blast him out with a fart. Her gassy winds would probably be enough to peel him off the sides of her butt cheeks, or even her asshole, right? She made a face and grunted, pushing the gas along...

----

When Nikki got up from her seat Mark's entire world turned over. Her smothering anal muscles began to relax, and all the anal juices lining her bowels started dripping downwards from gravity. Mark, still immobile within the thick slime, was just about to give in to the embrace of death when his head popped inside a frothy stink bubble. Miraculously finding somewhere to breathe in such a place, the shrunken boy coughed up gobs of slime and took his first heave of air in what felt like forever. It smelled like pure shit but he didn't care, he was still alive.

As the giant girl ran to the washroom her insides shook violently. The sticky slime had begun to form a pool near her exit hole, and was now sloshing around from her movements. Mark's minuscule body was stirred around in the flow of juices, and was pulled away from the bubble that was keeping him alive. Once again he was caught in a chaotic whirlpool of girl grease, left to drown. A thunderous quake rocked his body as Nikki sat down on the toilet seat. Everything went still for a few seconds as Mark's lungs screamed for air.

Eventually something screamed back. A low organic groan echoed through Nikki's bowels. The walls of her ass began to quiver. Still trapped under the heavy goo, Mark felt strong rumbles travel his way. Enormous bubbles of gas filled above the pool of slime, bloating the colon. The pressure built and built until the ass muscles squeezed down and forced it all out. Nikki's ass farted with a wet roar, blasting Mark downwards with the force of a rocket launch.

With a splash he hit the water, along with an eruption of Nikki's anal juices. All the slime that had been pooling inside her bowels sprayed out at once, along with the fermented gases that came from within. The gross glob Mark was encased in dissolved in the toilet water, finally freeing him. He tread water and felt cool air fill his lungs. It was so great! No more blistering heat, no more awful smell! He was finally free of Nikki's ass! Never before had Mark been so happy to have Nikki fart on him. He could see light again. Up above he was greeted by the girl's backside, and her spread drooling anus. Now he just needed her to see him.

Nikki's shoulders tensed as she felt how wet her fart was coming out. Was her ass really that wet? She could feel the remainder of runny slime dripping from her anus. Later she would need to wipe her butt cheeks with toilet paper to clean up. Before that though, was Mark okay? She needed to check the toilet for his shrunken body.

Getting off the seat Nikki turned around to place her head above to toilet. She recoiled a bit from her own smell. Man, her gas was bad today. Fanning it away she leaned closer, inspecting the water for any signs of her friend. He was below, waving his arms and yelling up to her giant face. But was he too small for her to see? Her next words sealed his fate...

"Oh... guess he's not there." her voice said.

Mark's heart froze in his chest. Was this actually it? Was he trapped in this awful place until he died? Even splashing the toilet water around as much as he could Nikki still couldn't see him?!

...

"Oh wait! I found you! Oh my god Mark I'm so sorry about that, I totally missed you there!" Nikki exclaimed.

The micro-sized boy breathed a huge sigh of relief. She noticed him. After being tortured by her farts and gargantuan asshole he had finally been spared from Nikki. Her unawareness to just how insanely small she had shrunken him down to had nearly killed him, but at long last he was saved. Even with the horrible stench surrounding him Mark smiled, almost chuckling to himself from how crazy this situation was. Maybe it was the adrenaline still rushing through him or it was the intense wave of emotions that he was feeling after finally being found, but he was happy instead of furious. Of course he knew Nikki didn't actually want to hurt him, it was just her carelessness was downright deadly.

"I'll get you out of there right away, okay?" Nikki said, looking straight down at him. "I had no idea that you were shrunken THAT small! I swear, I only meant to make you like an inch or two small, not... whatever the hell that is."

Mark wanted to tell her it was okay. Her voice was different than usual, she actually sounded concerned for his safety. After being teased so ruthlessly in her ass he was sort of expecting her to laugh at his toilet-drifting position, but that wasn't the case at all. The possibility of actually killing her friend with her ass must have crossed Nikki's mind, and it seems like she was still feeling rather shook. Mark looked at the enormous bowl surrounding him and felt relieved. Had Nikki been less careful he could have been in this toilet under much much more harrowing circumstances. The giant girl continued.

"I mean it's no wonder I didn't see you there the first time. You're so small now! You look just like you're a piece of lint in my panties."

What?

"Well I'm glad you were only stuck there and not inside my ass. Could you imagine how gross that'd be? You'd probably be swimming in that toilet right now."

"N... Nikki?" Mark stammered.

Nikki's face was so far away. For him it was easily several miles from her head to the bowl. Now that he looked at her closer, her line of sight wasn't quite looking down inside the toilet bowl at all. It was just outside of it. Nikki was looking down at her own panties between her legs, at a piece of lint she thought was Mark. Any thoughts of being saved were a lie, or rather just a huge mistake. Nikki had no idea where he was or how much serious peril he was in. She thought he was safe and sound in her underwear, not treading water in a utility for defecation.

Then the worst thing ever happened. She turned around.

"Now while I'm here I still have to use the toilet for a bit, okay? I'm sure you can tell from just being down there, but I'm a bit backed up." she said, talking to the lint. "I'll definitely get you out when I'm finished."

Nikki did a 180 and presented her huge wobbling ass to the bowl. Mark's expression creased in despair. He wanted to be in denial but her legs started to bend. She was going to relieve herself with him inside the toilet bowl. Her incredible sexy ass pushed itself outwards, descending with a massive heart-shaped shadow towards him. Mark could only look at it and whimper with fear. This couldn't actually be happening, right? Nikki's huge round butt cheeks opened themselves to the toilet bowl, naturally spreading apart to reveal her steamy crack within. A sticky line of anus drool oozed out in the open, dangling above as a fresh reminder of the horrors Mark had just gone through.

This was the first time he had seen Nikki's ass at this size in full. He had only been a passenger, one delegated to her crater-like anus, but never had he been able to see the entire thing in all it's beauty. Nikki's giant rear was just as plump and sexy as he could have imagined it would look naked, only now it came with the minor side effect that it was going to end his life. Her insanely massive booty was practically the size of the Moon compared to Mark, or more accurately two thick moons slapped together. The sheer size of such a thing falling down towards his microscopic body made him instinctively want to run and hide, but there was nowhere safe.

Without hesitation the girl's ass planted itself on the toilet seat, causing the whole bowl to tremor with her incredible weight. The enormous ceiling that was her ass crack wiggled into place, getting comfortable. It was surreal and frightening to see her ass prepare itself from this position, as her giant anus loomed over him. All the light from above was snuffed out, save for the bit coming underneath the seat's rim and between Nikki's legs. Mark could just barely make out her face through the bright opening, as she was looking down at her panties.

"There isn't really a good place to hold you so just stay there and be safe until I'm done. Um... I know you're already heard me fart and stuff but... it's still a bit embarrassing for me. Can you plug your ears until I'm finished?" She asked in a feminine voice.

Her anus began to undulate. The giant mass of wrinkles pulsated in and out at Mark. He watched in terror, knowing that this is how he was going to die. After all the things he went through, after surviving through her giant asshole's droning farts and her sticky bowels nearly drowning him in anal juices, all his struggles were now for naught. He had just barely pulled through being killed by her ass several times over, and now that he had made it through to the other side, this was how it was going to end. It felt like the weight of hopelessness was sinking him down into the toilet water. Nikki was going to use her mighty ass to shit all over him and there was nothing he could do to stop her.

The building pressure in her guts made deep groans as it traveled south. Her humongous anus bulged out, more and more it widened and flexed as it prepared itself for release. Low gurgles echoed from within her bowels, the sloshing hell Mark had been a part of just minutes ago was active with life once again. Finally, as her tremendous anus pushed one more time, a hot juicy fart came rushing out of it. Nikki's perfect asshole yawned open, spreading its plump greasy wrinkles apart to let the gas through. Despite how lazily her sphincter opened, the jet force of air shooting out of her colon was anything but relaxed. Her searing anal winds blasted into the bowl, erupting into the water like a giant hammer had come crashing down. Mark's spec of a body was caught in the epicenter of the blast, sent flying into a flurry of water and gassy fumes that threatened to drown him.

Nikki's fart made a loud blrrrrt noise as it exited her shapely butt, but from the perspective inside the bowl it was like a deafening foghorn followed by the mother of all shockwaves. The sound rebounded off the smooth porcelain walls, echoing with a meaty drone. The impact of the fart carried through the basin's surface, ripples washed back and forth long after the outburst had ended. To Mark these were akin to tidal waves, swallowing him up and dragging him underneath. The dizzying flow turned him over so many times he lost which way was up, and only found the surface by pure chance. It was like being inside a natural disaster, only it was the result of one of Nikki's farts. All her ass did was let out a little bit of pressure and it was able to totally overpower him.

As Mark caught his breath he wretched on the trademark scent of Nikki's gas. Her steamy anal air had polluted the entire bowl, and with her butt sitting firmly on the seat it didn't have much place to go. The burning odor pricked at Mark's insides like needles, he couldn't do anything but endure it. It smelled just as bad it did being stuck inside Nikki's immense anus, right after she had let out one of her awful butt bombs. Mark coughed and wheezed to get the gross stink out of his lungs, but it just wouldn't go away. Indifferent from his current suffering Nikki's anus puckered again. She pushed once more and let out a second massive fart.

The powerful eruption slammed down upon the waves just as it had before, only this time it was accompanied by something else. Flecks of anal juices that had drooled down Nikki's soft shit tunnel came spewing out with her potent gas, barraging the bowl with filthy shit rain. The gross mucousy substance hit the pool like bombs, exploding and splashing all around Mark. His minuscule body was flung through the rapids of Nikki's fart, swirling rapidly as the shotgun spread of gassy slime splattered everywhere. Nikki perked up from the sudden wetness and sputtery sound of her fart, slightly embarrassed that her tiny friend could hear it. What she didn't realize was that her tiny buddy was in the center of her ripe release, and everything she was pushing out of her giant ass was going straight to him.

By the time the disgusting rain was over the downpour had started. Nikki made a soft groan and her crotch burst with a stream of hot piss. The shocking pillar of liquid hit the waves like an earthquake, laughing at the pitiful ripples created by Nikki's fart and making enormous tsunamis instead. The yellow stinky urine expanded itself through the entire bowl, contorting Mark's hellish prison into a storm without end. Nikki's pussy continued to shoot the seemingly unending stream from it's peehole, indignant to the tiny boy's suffering underneath it. He could barely breathe without getting the sour discharge in his mouth, coupled with the still-lingering clouds of Nikki's farts. Struggle as he might, the waves were in control of where they carried his little particle of a body. At this point he could only pray and hope for a miracle.

But then he saw it. The current was about to pull him back underneath the waves. In a fleeting second of being above the surface he saw his executioner. Nikki's incredibly massive anus had grown to a size he had never witnessed before as it widened to let out a gigantic log of shit. Her anal wrinkles were stretched to their limits and had puffs of rank gas hissing through their folds, they pulling apart as far as possible to let the turd through. The impossibly huge chunk of shit was inching downwards, closer to Mark, and before he saw any more he was swept back underwater. He knew that in the next few seconds Nikki was working that colossal log out of her ass, flexing her anal muscles to push the huge beast out of her body. She was up there, clenching and relaxing her butthole, not knowing that her friend was about to be decimated by her crap. In only a couple more seconds he would be-

It was already out. The city-sized pillar of shit fell into the water like a floating island crashing down into the ocean. Nothing could stop it from catching Mark on its way down, even if he had ten more minutes to swim out of the way his tiny legs wouldn't have been able to carry him far enough. Instead the incredible log plastered his body to the side of its girth, like an errant piece of dirt, and pulled him all the way down to the bottom of the bowl. Nikki's ass relaxed with another loud fart up above, and began to push out her next shit, but by then Mark was already flattened and drowning at the floor of the toilet.

He was buried in his classmate's shit and had water filling up his lungs. There was no way out from this. Panic gave way to misery as he suffocated, but in the final few moments Mark found a brief sense of comfort. His clouded mind thought about Nikki's giant ass and what he went through. After all the horrible things her butt had done to him, he managed to die before it was done letting out all her turds. It was a petty victory... but at least he didn't have to endure more torture than he had to...

Nikki's sexy bottom finished letting out all her crap until she was empty. She wiped, disposed of the paper, and flushed unceremoniously. Mark's lifeless body was dragged into the plumbing with the rest of her feces, never to be seen again.

"Ahhh, I feel a lot better now." Nikki said out loud. "Sorry about that Mark, after sitting down I really needed to go. Now that I'm done I'll get you out of there now. Hang on tight!"

Still sitting on the toilet seat Nikki pulled her panties back up to her knees. She scooped her hand under the crotch area, pushing the part of the fabric that normally touched her butthole upwards from the other side. She needed to get her panties a lot closer to see Mark properly. Only he wasn't there.

"What the...?"

The small shape that she thought was Mark was right in front of her. The mistake was clear, unless her friend was suddenly very lint-shaped she had just made a grave error. Nikki's expression twisted into shock as she looked at the lint. She checked and doubled checked her panties, looking in any nook and cranny where Mark could be hiding. If he wasn't there then where was he? Could she have...?

After school Nikki checked her room and her bed in case she dropped him somewhere. She called Mark's phone over and over, but there wasn't any answer. He was gone, lost, and never coming back. Nikki didn't want to admit it to herself, but deep down she knew. She had turned her friend into toilet food.

"Mark! There you are! I'm so sorry!" her voice said.

The micro-sized boy breathed a huge sigh of relief. She noticed him. After being tortured by her farts and gargantuan asshole he had finally been spared from Nikki. Her unawareness to just how insanely small she had shrunken him down to had nearly killed him, but at long last he was saved. Even with the horrible stench surrounding him Mark smiled, almost chuckling to himself from how crazy this situation was. Maybe it was the adrenaline still rushing through him or it was the intense wave of emotions that he was feeling after finally being found, but he was happy instead of furious. Of course he knew Nikki didn't actually want to hurt him, it was just her carelessness was downright deadly.

"I'll get you out of there right away, okay?" Nikki said, looking straight down at him. "I had no idea that you were shrunken THAT small! I swear, I only meant to make you like an inch or two small, not... whatever the hell that is."

Mark wanted to tell her it was okay. Her voice was different than usual, she actually sounded concerned for his safety. After being teased so ruthlessly in her ass he was sort of expecting her to laugh at his toilet-drifting position, but that wasn't the case at all. The possibility of actually killing her friend with her ass must have crossed Nikki's mind, and it seems like she was still feeling rather shook. Mark looked at the enormous bowl surrounding him and felt relieved. Had Nikki been less careful he could have been in this toilet under much much more harrowing circumstances.

"Here, grab on to this!"

His giantess friend had unrolled a giant strip of toilet paper and lowered it down into the bowl. The paper dipped into the water, soaking itself immediately as it descended under the surface. Nikki wiggled it a bit towards Mark and lifted it back out, his minuscule speck of a body sticking to the damp material like fly paper. He didn't really need to hold on to anything, the tension of the gigantic water droplets held him in place just fine. After finally exiting the toilet Nikki brought the wet paper into her hands and carefully retrieved Mark's body by sticking him to the tip of her finger. Mark felt the cool air surrounding his naked body and began to shiver. Nikki gently examined the pad of her finger up close. It was scary to have her massive eyes looking at him, studying his almost invisibly-small shape. When she spoke it was loud like thunder.

"Holy shit you're so small now! How did you even survive? You were in my asshole the whole time right? Even when I was farting and squeezing it?! Jesus..."

The most she could see was Mark's puny head nodding in agreement.

"Ugh... I'm so sorry! I really didn't know I had made you that small! Seriously, I only wanted to make you like... the size of a toy or something! It was just to tease you. I swear!"

Mark nodded again, trying to get across that he understood.

"I don't really have anywhere I can keep you safe, so I'm just going to use the portal device to send you home okay?"

Using her other hand she fished the device out from her bag.

"Unless... you want to spend the rest of the day back in my ass again?"

Nikki's mouth frowned a little after making that joke. It was clear she felt bad immediately after the words came out of her mouth. She couldn't help herself from teasing Mark, it was in her nature or something.

After that she set the coordinates to exit the portal back at Mark's house, doubling checking to make sure the numbers were right this time. She had to reverse the sizes of the portals from how they were before, to make sure when he came back out he'd be the same height he started out as. Due to this, the portal was so small that Nikki couldn't really reach her finger all the way through. Instead, since she was still sitting on the toilet, she tried a "dropping" approach. The massive teen placed the small portal between her legs, at the stretched-out hammock of her panties. Mark looked down as she brought her finger closer, at the center of her gigantic underwear was a small whirling portal leading to one of the rooms in his house. Nikki waggled her finger a little, allowing Mark to drop down in free fall for a second, before landing back inside his house.

"Landing" might not have been the appropriate word for it, it was more like a painful crash onto the hard tiled floor. Nikki was considerate enough to send Mark back to the bathroom of his home, where he could start to clean himself up. Even so, the fall really hurt, and it took a couple seconds for him to stand back up. It wasn't nearly as bad as the torture he went through inside her giant anus, but his knees still ached. Thankfully his parents weren't home to hear the loud thud he made coming in.

Despite having a bath in toilet water, his body reeked to high heaven. He was only just freed from an unwanted tour of Nikki's bowels, the disgusting waste and slime that had nearly drowned him to death had imprinted its smell onto his skin. Being farted on by a school girl's ass thousands of times the size of your own body would do that to you. Mark took one whiff and nearly wretched, he needed several scrubs over to make himself feel clean again. Luckily the shower was right here.

Mark ran the water hot, really hot. He must have used up half a bottle of body soap, smearing himself in the bubbly, fragrant scents over and over again. He scrubbed so hard his skin felt almost raw. His hair was the hardest part, getting Nikki's fart stink out of that took at least 20 minutes alone. When he was finally done though he felt like a new man. He'd never had a shower that long and that focused, it felt like he had been the freshest in his life. The bathroom mirror was completely fogged up with steam as he dried himself off, the whole room was dripping with condensation thanks to the shower running so hot for so long.

Mark returned to his room to get dressed. There was still a faint trace of Nikki on him but he was confident it wasn't enough to stain his clothes. With a big sigh he laid down on his bed and started browsing his phone. It was only just the starting hours of the afternoon and yet he felt exhausted. Fighting for his life inside his friend's gigantic anus was a lot to go through. After a couple minutes he put his phone down and rested his eyes. Just a short nap was what he needed...

GGRRRRRGGLLLRRRGGG...

A tremendous sound jolted Mark back awake. It had been about a half an hour since he passed out. The bellowing noise sounded like an earthquake was happening around him. Right away he got up from his bed and looked around in confusion. His room was still how he remembered it, but something felt wrong. Whatever the noise was, it was coming from the bathroom, so Mark cautiously went to investigate.

The steam left over from his shower had since dissipated. Most of the mirror had become unfogged too, and what it revealed was something he wasn't mentally prepared for. Mark didn't notice it earlier thanks to all the shower steam but the portal Nikki had opened was still on and running. The whirling exit gateway was hanging there on the bathroom ceiling, and sitting on the other side was Nikki's colossal asshole. Since she placed the entrance portal at the bottom of her panties, when she put her underwear back on, it caused the tiny circular gateway to line up with the wrong place. Now Mark was staring at her huge anus once again. It was just as enormous in magnitude as it had been before, only now it was exposed to the vulnerable walls of his bathroom. Mark remembered just how gigantic her hole was from when he was caught inside of it. Her anus's width far exceeded the entry point of the portal, it was big enough to swallow his whole house and maybe the next few down the road. Unfortunately for him, where he was looking at right now was the dead center of her butthole, where all the oily wrinkles met into one dark crevice.

Suddenly the massive beast twitched. Its sticky folds clenched together just on the other side of the portal, making a gross wet smacking noise. Then right after that they bulged back outwards, pushing out even further than they had before. For the teenage girl on the other side this action wasn't even anything of note, her asshole muscles were shifting on such a small scale that it didn't even register in her mind. For Mark however this minor movement made his entire house shake. Framed photographs rattled against the walls, his toothbrush leaning inside its holder trembled with enough force that it did a little dance. Then came the noise. A deep groaning sound roared from the orifice above Mark. It gurgled loudly and angrily, even greater than when it had woken him up. Far beyond the twitching maw of Nikki's oily sphincter, her bowels were dealing with some large gastrointestinal pressure. The bubbling payload of air snaked its way through her sexy body, pushing past the many obstacles in her digestive system to seek a way out. Mark recognized the sound immediately and knew it wasn't an empty threat.

He ran back to his room and grabbed his phone. He dialed Nikki's number from her contact info, praying that she would pick up. While the phone rang he raced back to the bathroom where the giant anus was still waiting. There was no answer. Shit. He tried texting her, all caps: "TURN OFF THE PORTAL NOW!!!" Sent. Anxiously Mark waited for a reply, sweating with the phone in his hands and the ridiculously oversized butthole looming above. The seconds went by agonizingly slow, reaching a full minute until Mark came to terms that Nikki wasn't looking at her phone at all.

At school, Nikki's phone was currently zipped inside her bag. The emergency toilet meeting she had with Mark resulted in her running late for class, and so she stuffed her phone away with her books without even realizing. The phone silently vibrated when he called, and when he sent her a text the notification light flashed for no one to see. Meanwhile Nikki was sitting at her desk, paying attention in class without being the least bit aware of Mark's predicament. Her huge shapely ass was pressed down comfortably into her seat, while her cute panties were formed flat against her buttcrack. There were no signs of her getting up to go anywhere soon, her asshole and the tiny portal underneath it were locked in place under the weight of her giant body.

Mark didn't know how else he could contact Nikki. If he didn't do something fast her anus was going to blast his house with a mega-sized fart. Another rumbling growl came from Nikki's ass, this one sounded serious. Back at school she felt her stomach gurgle a little. She put a hand to her tummy and felt the familiar pressure rising deep within her insides. All she had to do was push her hand a bit and the gurgling noises returned. A heavy weight entered her bowels, and she knew that a fart was coming. Her anus clenched in anticipation. She was still in the middle of class and she had to be careful. Nikki knew how to let her gas out quietly during lessons, but she had to focus her ass muscles to do it right. Meanwhile Mark's notification message on her phone was still blinking inside her bag.

The young man's bathroom shook even harder as Nikki began to focus on her butthole. The incredible lumpy folds of her anus tightened together inside her panties, exerting strength onto the entrance to the portal, and by extension Mark's whole house. Objects were shaking and falling all over the place, but there was no time to pick them up. Mark needed to get Nikki's attention more than anything else. He stood on top of the bathroom counter, his feet planted on either side of the sink, reaching his arms up to go through the portal. Just on the other side Nikki's anus was flexing, holding itself closed as the gas filled up. Back in her classroom her large butt purred into the chair. Hot gurgles of methane were passing through her colon, underneath her skirt a whole cacophony of bubbly fumes were collecting together. Nikki could feel that the gas was nearly at her backdoor, it was almost ready to come out...

Mark's hands went through the other side of the portal, touching Nikki's twitching anus. He grabbed one of her meaty anal wrinkles with both hands, it was oily and thick and moving with a mind of its own. The hulking band of flesh throbbed and pulsated with the rest, clenching together with the other ripe folds to keep her hole shut tight. Mark could barely keep his grip on the girl's hot flesh, he squeezed and pulled at it as hard as he could, but his minuscule struggles didn't even register to his giantess friend. Her enormous butthole continued to flex and tighten as if he wasn't there. Mark grew desperate and wild. He needed to get her attention NOW.

He thrashed and pounded at the resilient flesh mounds, battering them as well as he could muster without falling off the bathroom counter. With open palms he slapped the girl's meaty skin, jabbing and hitting it while screaming for her to notice. In desperation he grabbed onto the anal wrinkle and held it as tight as possible, kicking his legs off the bathroom counter to yank it down with his full body weight. The natural sweat of her ass made it hard to grip but Mark hung on regardless.

Just then the giant anus started to let up. Mark thought it was finally succumbing to his attack but then the whole thing puckered outwards. Nikki's fat beefy wrinkles expanded flagrantly from her ass, the sudden shift in form caused Mark to lose his grip. He fell down to the bathroom's floor tiles, bashing his hip off the counter on his way down. Nikki's farthole bulged out towards him, her puckered anal folds domed out so far that they came through the other side of the portal. Mark's house creaked as the brewing storm shuddered through Nikki's ass, the buildup of pressure had reached its limit. Nikki leaned her massive ass back into her chair and prepared herself for release. Her mouth closed shut as she held her breath, focusing all her attention on relaxing her asshole just slightly...

Absolute hell burst through the portal and into Mark's house. The raging inferno of teenage girl gas blasted the door to his bathroom wide open, knocking it right off its hinges. The window going outside shattered into pieces, the shower curtain was ripped clean off, and Mark's poor body was slammed down into the hard tiles once again. Nikki's hot misty fart sprayed all over the place, violently erupting out of the portal and shooting her rancid gas throughout her friend's house. She was just parting her anal lips a little, carefully widening her asshole so that her fart would come out quietly, but the result came tearing visciously through the other side. Paintings flew off the walls, dishes fell to the floor and shattered, the whole building was vibrating from her gas, and it just wouldn't stop.

The tremendous fart droned on, flattening Mark against the floor. He couldn't move an inch as his friend let her gas out, the rampaging anal winds blew so hard that it felt like he was being crushed by them. Nikki's release was hot and potent, the muggy shittty air that had been cooking inside her bowels for hours was now brazenly spreading through the rooms of his home. It smelled atrocious, her breakfast smoothie, eggs, and toast had all been transformed into a steamy powerful bout of gas that couldn't be stopped. Bits of moisture sprayed all over Mark's body, splattering the bathroom walls. The heat was sweltering, it was so hot that it made the bars of soap start to melt. Nikki sighed as she let it all out. Her gas was hissing out quietly like she hoped, and the release of pressure felt comforting to her butt.

After a few more grueling seconds she was done, and her asshole closed back up. Mark's house was left a disaster zone, it reeked to high heaven and the damage was strewn about everywhere. As he weakly stood up from the spot where he had been pinned down he noticed a dip in the floor. Nikki's fart was so intense it actually bent the bathroom tiles, creating a wide bowl in the floor where it had touched down. Mark coughed and gagged on the terrible stench, it burned at his lungs. Slowly he limped himself around the house, opening all the windows to let Nikki's gas air out. He needed to have another long shower to get her smell off him again, but first he needed to clean the house before his parents got home.

The next several hours were spent picking up everything that had been knocked over and broken because of the fart. Mark cleaned room by room, fixing all the major problems before finally cleaning himself off. The raw air from Nikki's ass started to filter out after a couple hours, but the lingering stink would remain for days. A heaping amount of cleaning products were going to be needed to get things smelling fresh again. When his shower was done he went back to tidying, taking all the broken pieces of stuff and putting them in large garbage bags. His nose became dull to the stink after a while, but it didn't actually make the situation better. When his dad came home he was furious, and when his mom came home she nearly threw up.

----

"Here it is," Nikki said, handing the portal device back to Mark.

It was the next day and the two of them were heading to school together. Thankfully after the one fart Nikki checked her phone and saw Mark's message. It might have been entirely too late, but she was able to close the portal before any more damage was accidentally caused.

"I probably could have farted again too," she said to him. "I thought about letting out some more in class after that first one, but I didn't want it to smell too bad around me, y'know?"

"Yeah." Mark said plainly as he put the device safely inside his bag. His tone seemed a bit upset.

"Hey..." Nikki said in a concerned voice, "I'm really sorry about what happened yesterday. I honestly meant to just play a little joke on you, and I had no idea the portal was still open after all that happened. I don't know how to fix things, but if there's anything I can do-"

"Stop." Mark interrupted. "It's... okay. You don't have to worry about it, really. It was just an accident. I told my parents I was working with some chemicals in the bathroom and accidentally went overboard. They think the... smell is just part of some science experiment gone wrong."

"Really? Are you sure?" she said.

"Yeah."

"...Phew! That's a relief! I seriously thought you were going to be mad at me there. Ah, thank god!" Nikki cheered, going back to her old self. "So what about all the damage though? Are you covered by insurance or something?"

"Probably not." Mark said flatly. "But it's alright. I figured I might sell a bit of this tech to a portal security company or something. Remember how you were worried about someone accessing your receiver without permission? They'll probably pay top dollar to know how I can hack their systems so easily. That'll be more than enough to repair the bathroom floor and replace the stuff that got broken."

"Wow, good idea!" Nikki said, legitimately impressed. "How NOBLE of you, using your powers for good instead of evil," she joked.

"I don't know about that, I mean I'm still doing it for my own benefit, aren't I?" he said back.

"Just shut up and take the compliment!" Nikki laughed.

Things seemed to be back to normal. Nikki was in a better mood since Mark assured her things were going to be okay. He could tell that she was actually worried about him yesterday too, and because of that he didn't feel any anger or resentment. The two of them continued to walk to their classes together, like nothing had ever happened.

"So..." Nikki began, "what are you going to do with the portal device now?"

"Huh?" Mark reacted.

"Well, I mean you just got it back. You probably had a lot more experiments you wanted to try out with it, right?"

She wasn't wrong. Mark still had a list of things he wanted to test but never had a chance to yet. Nikki continued.

"I'm just saying... I don't mind helping you out. Things didn't exactly go as planned yesterday, but if you want to use it with me again sometime I promise I'll be more careful."

Mark thought he was hearing things. Despite everything that happened, all the horrible disgusting ass torture he went through, Nikki still wanted to try it again. He had nearly died and had his house blown up and she was asking him this. She actually was. Mark looked at her in disbelief and she only smiled back. Today Nikki was wearing a soft cotton shirt and black leggings. The smooth dark material hugged her ample curves like a second skin, leaving next to nothing to the imagination. Mark desperately wanted to tell her no, every thought in his brain was blaring with warning sirens. But still...

"...I'll think about it." he said.