I never meant for it to happen, but once my little sister turned eighteen she started walking around the house in nothing but those tiny tank tops and panties, and the way she looked at me when dad was at work made my cock twitch every damn time. I was nineteen, supposed to be the responsible one, but fuck that. She was reluctant at first, always saying "we shouldn't" while her body told a different story.
It started on a hot afternoon when the AC was busted. She came out of her room in just a thong and a cropped shirt that barely covered her tits. "Stop staring, perv," she muttered, but she didn't cover up. I was on the couch, hard already, and I told her straight, "Come here and sit on my lap if you want to act like that." She hesitated, cheeks red, but she did it. My dick pressed right against her ass through my shorts. She squirmed but didn't get off.
"Bro, this is wrong," she whispered, but her hips rocked a little. I reached around and grabbed her tits, squeezing hard. "Then why are your nipples so fucking hard?" I yanked the shirt up and sucked one into my mouth. She gasped, trying to push my head away, but her thighs squeezed together. "We can't… mom could come home." I didn't care. I slid my hand down her panties and found her soaked. "You're dripping for your brother, you little slut." She moaned despite herself as I rubbed her clit in circles, rough and fast.
She kept protesting, "No, stop, this is incest," but her pussy clenched around my fingers when I shoved two inside her. I finger-fucked her right there on the couch until she came, shaking and biting her lip to stay quiet. After that she tried to avoid me, but every night I'd catch her in the hallway or the kitchen. "Just once more," I'd growl, pinning her against the wall. She'd say "this has to be the last time" while reaching for my cock and stroking it.
One night dad was out late. I went to her room and she was in bed pretending to sleep. I pulled the covers off and spread her legs.
"No, not tonight," she whimpered, but her panties were already wet. I ripped them aside and buried my face in her cunt, licking her deep and sucking her clit until she was bucking against my mouth. "You taste so good, sis." She came hard, then tried to close her legs. "We really can't keep doing this."
I flipped her onto her stomach, pulled her ass up, and slammed my cock into her tight pussy in one thrust. She cried out, "Fuck, it's too big," but pushed back against me. I pounded her hard, slapping her ass, telling her how her reluctant little hole was sucking me in. "You're my free use slut now." She came again, moaning my name, then begged me to pull out. I didn't. I filled her up, watching my cum leak out of her.
After that it became our routine. She'd act shy and reluctant every time, whispering "someone will hear" or "this is so wrong" while I bent her over the kitchen table, fucked her in the shower, or made her ride me on the living room floor. Her protests always turned into desperate moans once my dick was inside her. She'd come on my cock over and over, then afterward she'd say it had to stop, but the next day she'd be back in those tiny panties, waiting.
By the end of the summer she stopped pretending as much. She'd just bend over and spread herself open, still muttering "we shouldn't" while I fucked her raw and filled her again. It was dirty, wrong, and the hottest thing either of us had ever done. We both knew it wasn't ending anytime soon.
