"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...