"Stop grabbing my ass!" my sister said, squirming as I cupped a generous handful of her firm, tanned butt.

I waited a few moments, until she returned her attention to the soccer game on TV, then I reached up again and spread my palm across her right cheek. I squeezed and groped my teenage sister's plump rump while she tried her best to ignore me.

I crept closer and closer to her on the bed, until my upper body was draped across her back. We were both shirtless and my chest and stomach pressed against her warm, soft lower back.

Off to one side, the roach from the joint we had shared sat forgotten in a smudged glass ashtray. "Come on," I said, "mom and dad won't be home for hours. Let's fool around."

"Urrrrgh," my sister moaned, a touch melodramatically. "Why do I even smoke with you? You always get so fucking horny!"

"I bet I'm not the only one," I said, pressing the growing bulge in my underwear against her panty-clad ass. I pumped my hips slowly, dragging my clothed cock up and down her ass.

"Fuuuuck," my sister moaned, her face pressed into the bed. When I slid my fingers into the waistband of her panties and tugged them down, she didn't stop me. She kept her eyes focused on the TV, but I could her her shallow breathing.

I rolled down my sister's underwear with slow, deliberate care. I bent in close, letting her feel my breath on her round bottom. She stiffened and goosebumps raised on her skin.

I raised myself to my knees and tugged down my briefs. I held my swollen cock in one hand, letting it grow to a full seven-inch erection. My sister glanced back over her shoulder and quickly buried her face in the bedspread again. The unspoken rule seemed to be, as long as I don't acknowledge him, we're not doing anything wrong.

I tugged the panties down a little further, revealing the top of her pink slit. It was puffy, dewy with moisture. My sister was as visibly aroused as I was. She said breathily and deliberately, "Don't fuck me."

I reached over to the nightstand, grabbed a bottle of lotion, and squirted some on my fingers. I pressed them between my sister's asscheeks, rubbing them up and down her virgin crack. She moaned as my long, square fingers rubbed her dark cleft. I grasped my cock and bounced it up and down, slapping it off my sister's ass with a soft "thwack, thwack!" She giggled.

I took a double handful of my sister's ass, spread her slightly, and threaded my cock between her globes like a hotdog in a bun. I squeezed her buttocks back together, sandwiching my prick, and began to thrust. The tip of my cock slid in and out the far side of her ass, occasionally bumping against the small of her back.

The pace of the soccer game began to speed up as one team drove for the goal. She moaned quietly, finding it harder to concentrate on the TV, but she never turned around. As the center ran towards the goal my strokes increased in speed, my cock gliding in and out of the well-lubed channel between my sister's lower cheeks.

I started to grunt with pleasure. "Umm, fuck, fuck!" I moaned. She moaned in time with me and started to hump back. The crotch of her panties, the part that still covered her pussy, was soaked. "Fuck, I've gotta cum," I announced. She said nothing.

As the center lined up his shot, my prick burst. Ropes of hot jizz shot across her ass and up her back. I kept cumming for what seemed like forever, pumping out blast after blast until my aching balls were completely empty. Exhausted, I sat back to survey the damage.

My sister was spattered from ass to shoulder, crisscrossed with streaks of pearly cum. She lay facedown, no longer watching the game, just breathing hard. Her skin was flushed. She was quiet for a little while, and then she finally spoke. "How'd that feel?" she asked.

"Mmm," I moaned. "Fucking awesome." I squeezed her thighs, my hands coming close to the soaked triangle of fabric between her legs.

"Good," she said.