She bent over the bed and wiggled her ass at him, already wet and ready. "Fuck me hard," she said, looking back. He didn't waste time. He grabbed her hips, lined up his thick cock, and slammed it straight into her pussy in one rough thrust. She grunted as he started pounding, skin slapping loud and fast.
Her ass felt normal at first, just jiggling with every slam of his hips. But then the heat hit. A strange tingle spread through her cheeks, and they started to swell. Right there on his cock, her ass grew bigger. Each thrust pumped it up a little more, the flesh expanding outward, getting rounder, heavier, softer.
She moaned, feeling the extra weight pull at her.
"Shit, it's happening again," she gasped, but she pushed back harder instead of stopping. Her ass ballooned another inch, then two. The skin stretched tight and shiny. He noticed and growled, "Fuck, your ass is blowing up." He slapped one cheek and watched it wobble bigger than before.
He fucked her faster, driving deep. Every time his balls slapped against her, her ass expanded more. It grew round and huge, cheeks spreading wider, the crack deepening. She reached back and grabbed handfuls of the new flesh, squeezing as it kept inflating. The sensitivity shot through her. Every slap, every thrust sent shocks straight to her clit.
Her pussy clenched around him, dripping down her thighs. The growth made her feel filthy and full. "Bigger," she begged. "Make it bigger." He grabbed the expanding cheeks, fingers sinking into the soft, growing meat, and rammed harder. Her ass surged again, swelling like it was being pumped full of air and cum at the same time. It jiggled wildly now, heavy and massive, smacking against his stomach.
She came hard, legs shaking, but he didn't stop. He flipped her onto her back, lifted her thicker legs, and shoved back inside. Her ass kept growing beneath her, lifting her hips higher off the bed as it ballooned outward. The new size made her feel exposed and slutty. She reached down, rubbed her swollen clit while watching her own ass expand another size.
He pulled out, flipped her again, and buried his face between the massive cheeks. He licked and bit the sensitive skin that had just grown. She screamed when he spread them wide and tongue-fucked her ass. The expansion slowed but didn't stop completely, her cheeks still plumping up slowly with every moan.
When he finally shoved his cock back in, her ass was enormous, wide enough that his hands couldn't span it. He fucked her like an animal, using the new handles of flesh to pull her onto him. She came again, then again, each orgasm making the last few inches of growth hit. Her ass settled huge and perfect, wobbling with every thrust.
He pulled out at the end and painted the massive cheeks with thick ropes of cum. She lay there panting, ass so big she could barely reach around it, still twitching and sensitive. He rubbed his load into the new skin and gave it one last hard slap. She smiled, already thinking about the next time she'd make it grow even more.
