"No! Nooo!" you shouted.

Gwen stood up and started to take her underwear off. She unhitched her bra and let her tits come out. They weren't the biggest, but they were huge compared to you. Then she pulled down her panties. You could smell her girlish musk from where you were in her hand, it was strong. Katie and Ellie excitedly took off their underwear too, they were looking forward to humiliating you.

Once they were all done Gwen crawled on top of her bed. She bent over, sticking out her round ass. The hand she was holding you in slowly moved towards it. You looked and the other girls, begging them for help but they wouldn't listen. They were both watching intently, eager to see you be punished by Gwen's huge ass. You turned back to see your sister's enormous buttocks in front of your face. This was really happening.

"Since I'm his sister it's only right that I get to go first. You girls can each get a turn with him after, okay?" she said.

"Gwen! Stop this!" you screamed.

With her other hand she pulled her butt cheeks apart. The juicy curves separated, revealing the slick and sweaty ass crack inside. Dead center in the middle was her asshole, glistening in the light. You already had the misfortune of seeing it many times before, when Gwen would torment you with her ass. This time was different though, it was huge. Every detail of her wrinkled hole stood out, like it was under a magnifying glass. She had a single freckle on the outside of her hole, now it was the size of a big round car tire. The anus twitched as she drew you closer to it, like it was a big pair of hungry lips smacking together. She could feel your tiny arms trying to fight back against her hand, but that wasn't enough to make her stop.

Your face was abruptly pressed into your sister's asshole. It was warm, almost hot to the touch, and seemed to clench upon feeling you. The greasy skin pulsated against your face, staining you with stinky oils. Gwen's dirty anus smelled much worse up close, the dull scent of sweat was mixed into the rank stench of old farts. Using her hand, she rubbed you all over her rubbery pucker, your nose stuck between her folds. A powerful finger pressed into the back of your skull, wedging you deeper into her winking brown-eye.

"Come on big bro, you should be used to my butthole by now. I made you lick it last week afterall." Gwen mentioned as she continued to flex her anal muscles. "Start licking, or I'll make you taste what's inside!" she commanded.

You really didn't want your tongue going anywhere near your sister's asshole, but the alternative she gave you wasn't pretty. You winced and stuck your tongue out, weakly licking the gruesome skin. It tasted horrible, you gagged but kept going. Awful slime and sweat stuck to your taste buds. It was raw, the rancid feeling made your eyes water and cry. Gwen cooed and moaned softly, taking great pleasure from you licking her ass. Her friends laughed out loud, amused by you turning into their butt slave so easily.

"I can't believe he's really doing it!" Katie said. "I can't wait for my turn!"

You didn't want to think about licking hers next. This was already bad enough. You didn't even want to think about what you were doing right now. It was too gross, if you didn't focus on it you could maybe think about something else. Anything to clear you mind of the current situation. Gwen's bootyhole throbbed and flexed, and she pushed you a little deeper into it. Hot sticky oils soaked into your cheeks, your body was coated in that butt-stink you fear everytime your parents leave. It was impossible, no matter how hard your mind thought, the giant anus pulsating against your head couldn't be ignored. Your younger sister's massive folds squeezed around your tongue, sinking it between two juicy lumps of meat. You tasted her caked-in filth and screamed.

"You enjoying yourself down there brother? You're so pathetic, licking my asshole. Eat it up like it's the best meal you'll ever get. That's right, you should count yourself lucky. No girl would ever let you touch her intimate parts like this, especially any as hot as me!"

Her asshole twitched some more, happily pulsating against your face. You tried to push back with your hands to free yourself but your tiny little fingers just sank into the supple flesh. Up above Gwen laughed. Her anus planted itself around your head, locking you against the flesh of her sphincter. Suddenly a huge fart burst from her butthole, blasting you with a steamy spray of gas. Hot anal fumes shot inside your mouth and up your nose. Gwen had farted on your before, many times right on your face, but those were nothing compared to this. The amount of gas shooting through her body was unbelievable, it was like a hurricane. Her huge asshole rumbled against your tiny head, its wrinkles vibrating as the fart poured out. The stench was thick and rotten, it had been fermenting inside her bowels for hours. The oily taste of her freckled asshole was like honey in comparison to her thick farts.

All three girls erupted into laughter. They had just watched Gwen's anus open up in front of your tiny head and blast you with her fart. It was comical, and utterly humiliating for you. Even after the fart had ended, you were still coughing on the smelly aftermath, yelling at Gwen to let you go. Your sister didn't pay attention and instead pressed you back into her rubbery hole, still red hot from the fart. All you could do was struggle against your younger sister's anus with a mouthful of her filthy flesh, desperately trying to breathe in any fresh air you could find. It was horrible, her burning smell was everywhere, stinging your nose. The anus twitched from your struggles, your sister enjoyed the tiny tickles you were giving her.

"Oh man, that was hilarious!" Katie said, catching her breath after laughing so hard. "Give him to me next, I think I can feel some farts coming."

"Sure." Gwen said, satisfied with the gassy punishment she gave you.  "After all, he is supposed to watch all of us tonight..."