Shane and his older step-sister Michelle had been fighting over who deserved to use most of the internet bandwidth while their parents were out meeting friends when things began to get heated. He called her ‘a flat-ass slut’ and she mocked his ‘tiny penis’, so the two of them stormed off into their rooms to sulk. Little did they know that just outside the window a fairy was listening in, plotting a way to teach them a lesson that would get them to appreciate each other. Sitting at his desk, Shane suddenly found himself in his step-sister’s room, laying on her bed looking at her phone. Feeling her dark hair around his face, he stood up and walked over to the bathroom mirror, gasping in shock as he saw Michelle in his own reflection!

Feeling her smooth, tan skin and briefly groping her soft C-cup breasts, he reached down and felt for the empty face between his legs when he noticed his hips were nothing short of enormous. “Look at how huge my ass is!” Shane complained to himself, lugging his enormous pumpkin-sized booty onto the counter of the bathroom and taking a photo of his giant cheeks. Her thong which had once given her some level of modesty was wedged tight within his giant cheeks, ready to snap at any second. Looking down at his thick, trunk-sized thighs as his feet dangled in the air, he realized that at some point, her ‘flat ass’ had become the biggest ‘phat ass’ he had ever seen!

“What the fuck?” he heard his old voice say, as Shane turned to see his former body staring at him confused, which now towered over his tiny 5‘ frame. “Did we just swap bodies?” Shane nodded dumbfoundedly, unable to take his eyes off of the enormous bulge he could see in his old jeans. “Let’s talk in the kitchen.”

The two of them walked down to the kitchen, Shane’s colossal, swaying ass almost knocking things off shelves unwieldedly. “It looks like something happened that swapped us and somehow... changed us.” said Michelle as she gestured at what had once been her relatively unimpressive backside, which now covered more than an entire seat. “And, uh, well...  it turns out I was wrong for saying you had such a tiny cock...”

“Can I see it?” said Shane, curious at how big the bulge could possibly be. Noticing his step-sister’ hesitation, he continued, “C’mon, it’s my own dick. I’ve seen it a million times before.” Reluctantly pulling down her pants, Shane was surprised as a rock-hard cock at least a foot long and wide as an energy drink sprung from her boxers! “No wonder you were nervous! This fat ass is turning you on!”

Michelle blushed, reaching to tuck it away again. “Stop laughing!”

“Sorry, it’s just so big... I’m curious about what it feels like...” muttered Shane, getting onto his knees and holding it’s enormous length in his hands. Without thinking he brought it to his mouth and licked it, sending a rush of lust through both their bodies. Before long he was stretching his jaw to the limit, gagging on as much of the cock’s length as he could without choking.

“I wanna... I wanna stick it in your pussy...” Michelle mentioned between moans, and without skipping a beat her brother turned his body around, pressing his ass and wiggling it against his shaft.

“...Then stick it in...” Shane said in approval, snapping his thong to fully reveal his snatch. “Just push forward and-AHHHHH! That’s my ass you... ungh...” Shane’s eyes rolled into the back of his head as his sister pushed further into his asshole, clouding his mind with intense please. “Don’t stop!”

Suddenly they both heard the front door open. “Kids, we’re home!” said Shane’s mother, coming into the kitchen and seeing her son sitting at the table, squirming in his seat while struggling to read a newspaper. “How was your night?”

“G-good....” Michelle sputtered, trying to disguise her pleasure. Meanwhile a butt-naked Shane stood on all fours under the table, stifling every urge to scream in pleasure as his step-sister continued to fuck his ass. As he felt the cock tighten up as his own mind reached orgasm, he covered his mouth in fear, knowing that if he was caught having sex with his step-sister in his former body, the two of them would have a lot to explain. In fact, even just the huge ass expansion would probably be too much for them to handle. Feeling an intense wave of pleasure fill his body in orgasm as his asshole filled with semen, and Michelle experienced her first time as cumming a man, they both decided that as long  as they could secretly fuck like this every single day, nothing else mattered. Outside the window, a fairy watched as her victims successfully hid themselves and went upstairs for round two, satisfied at creating another happy ending.