We were both adults, me twenty-three and my sister Lena twenty-one, but that never stopped the heat from building in our cramped apartment. It started as a stupid game after too many drinks. Lena dared me to give her a back rub on the living room floor, her tank top hiked up and her shorts riding low on her hips.
She was on her stomach, ass up just a little, laughing as I straddled her thighs. My cock was already half-hard from the sight of her smooth skin, and when I leaned forward to work her shoulders, it pressed right against the cleft of her ass through my jeans.
"Fuck, watch it," she muttered, but she didn't move away. Instead she pushed back a little, grinding that round ass against my bulge like it was an accident too. I froze, hands still on her back, but my hips twitched on their own. The zipper of my jeans caught on the thin fabric of her shorts, and before I could stop, I was rocking harder, dry-humping her like some desperate teen.
"Jesus, bro, you're really into this," she said, voice low and teasing. She reached back and tugged her shorts down just enough to bare the top of her cheeks. "Keep going if you want. It's not like we're doing anything."
That was the lie we told ourselves. My hands slid down, fingers digging into her hips as I yanked my cock out. It slapped hot and heavy against her bare skin, the head already leaking. She spread her legs wider on the rug, and I slid forward, meaning to just rub along her crack like before. But she was wet, slick from the heat of it, and when I thrust, my cock slipped straight between her pussy lips instead of over them.
We both gasped at the same time. The head popped inside her tight cunt with a wet sound, no condom, nothing between us. Lena's walls clenched around me, hot and dripping, and she shoved back hard, taking another inch before either of us could think.
"Shit, that's an accident," she panted, but she didn't pull off. Her pussy fluttered, sucking me deeper, and I bottomed out with a groan, balls pressed to her clit. "Fuck, you're inside me. Pull out."
I tried. I really did. My hips drew back slow, dragging my thick shaft along her slick walls, but she squeezed down and I slammed forward again on instinct. The slap of skin filled the room. She was soaked, juices coating my cock and dripping down her thighs as I started fucking her in short, rough strokes.
"Don't stop now," she hissed, voice turning filthy. "Accident or not, your dick feels too good. Pound that sister pussy."
I grabbed her hair and yanked her head back, driving in balls-deep with every thrust. Her cunt gripped me like a fist, milking every inch as I railed her on the floor. Sweat slicked our bodies, the wet squelch of her dripping hole echoing with each slam. Lena reached between her legs to rub her clit, fingers brushing my shaft as it pistoned in and out.
"Harder, make it count since we're already fucked," she moaned. I flipped her onto her back, hooked her legs over my shoulders, and speared her again. Her tits bounced with every brutal thrust, nipples hard as I leaned down to suck one into my mouth. She tasted like salt and need, her pussy spasming around me.
We didn't talk about stopping anymore. It was raw and messy, her juices splashing every time I bottomed out. I flipped her again, this time onto all fours, and spread her ass cheeks to watch my cock disappear into her stretched hole. Her asshole winked above it, and I spat on it, rubbing my thumb over the tight ring while I fucked her cunt senseless.
Lena came first, screaming into the couch cushion as her pussy clamped down, squirting around my cock in hot pulses. That pushed me over. I buried myself to the hilt and unloaded, thick ropes of cum flooding her unprotected depths. We stayed locked together, panting, my cock twitching as it pumped the last drops into her overflowing cunt.
After, we didn't move. My cum leaked out around my softening dick, running down her thighs in sticky trails. She looked back at me with a dirty grin.
"Accident my ass," she said. "Round two in the shower?"
We didn't make it to the shower. I pulled out slow, watching my load drip from her swollen pussy, then flipped her and shoved back in while she was still sensitive. This time it was slower but just as filthy, her legs wrapped around me as I ground deep, stirring my cum inside her. She clawed my back, begging for more, telling me how wrong it felt and how much she wanted it anyway.
We spent the night like that, switching positions on every surface. On the kitchen counter she rode me reverse, ass bouncing while she reached back to spread her cheeks and show me her cum-stuffed hole. Against the wall I held her up, her tits mashed to my chest as I fucked upward into her greedy cunt. By morning we were sore, covered in sweat and dried cum, but neither of us called it an accident again.
It became our secret. Every time we slipped, it was on purpose now, raw and direct, her begging for my load and me giving it to her every time. The taboo only made the orgasms hit harder, her pussy always ready, always dripping for the next forbidden thrust.
