I still remember the exact moment it crossed the line. My girlfriend Lisa had left for a work trip that morning, and her younger sister Rachel showed up at our apartment door around eight that night, saying she needed to crash because her roommate had thrown a party. Rachel was twenty-one, same as Lisa, with the same dark hair but curvier hips and a mouth that always looked like it was holding back a smirk. I let her in without thinking twice.
We drank cheap whiskey on the couch while some movie played in the background. Rachel kicked off her shoes and tucked her feet under her, the hem of her shorts riding high on her thighs. Conversation drifted from Lisa to work to nothing important. Then she leaned closer to refill my glass and her breast brushed my arm. Neither of us pulled away.
You always stare at me when Lisas not looking, she said, voice low and direct.
I didnt deny it. My cock was already half-hard from the whiskey and the heat of her leg against mine. You know exactly what youre doing.
Rachel set the bottle down, climbed into my lap without asking, and ground down once, slow. Then do something about it.
Her shorts were thin cotton. I slid my hands under them and found she wasnt wearing anything underneath. Two fingers sank into her wet cunt on the first push. She was tight, hot, and she moaned right against my ear like shed been waiting for this. I pumped my fingers while my thumb worked her clit, and she rode my hand until her thighs shook.
Bedroom, she said, breath ragged. Now.
We didnt make it that far. I bent her over the arm of the couch, yanked her shorts down to her knees, and freed my cock. One thrust and I was buried to the hilt inside my girlfriends sister. She was slick enough that I slid in easy, but she still gasped at the stretch. I gripped her hips and fucked her hard, the slap of skin loud in the quiet apartment. Rachel pushed back to meet every stroke, telling me to go deeper, to use her.
I pulled out, flipped her onto her back on the couch, and shoved her knees to her chest. Her pussy was pink and swollen, glistening. I drove back in and watched her tits bounce with every thrust. She reached down to rub her clit while I pounded her, eyes locked on mine.
Lisa cant know, she panted. But Ive wanted your cock for months.
That confession made me fuck her faster. I leaned down and sucked one nipple into my mouth, biting just enough to make her cry out. Her cunt clenched around me when she came, pulsing hard, juices running down my balls. I didnt stop. I kept slamming into her through the aftershocks until my own orgasm hit, pumping thick loads deep inside her.
We stayed locked together for a minute, breathing heavy. Then Rachel smiled that same smirk and said, Round two in the shower?
We fucked twice more that nightonce against the tiled wall with hot water beating down on us, her leg hooked over my arm, and again in Lisas bed with Rachel riding me reverse so I could watch her ass bounce. She came on my cock both times, loud and filthy, telling me how much better I felt than any guy her age.
By morning she was gone, sheets changed, no evidence left except the ache in my balls and the memory of how tight her cunt had been. Lisa came home the next evening none the wiser. Rachel still visits when her sisters out of town. We dont talk about it. We just fuck.
Every single time.
