I began to sigh audibly as she rose and fell. I could feel the cum churning; the first tightening of my dick that told me I wouldn’t last much longer. “Oh, my god,” I whispered. “You feel so good.” She smiled down at me and raised an eyebrow.
“You gonna cum, baby?”
I hesitated before answering “Do you think you can? Really quick?”
She did one of those coy, sidelong “Hmmm” faces, and then shrugged. “Why don’t you stand up,” she prompted, dismounting. I sighed in pleasure and dejection as her pussy slid off of me, but stood nonetheless. She bent forward on her knees and elbows, arching her back and pulling her hair over one shoulder. “Fuck me like this.”
I did, of course. I guided myself inside her and sighed with pleasure as her lips gripped me, holding tight as I began moving in and out. She started moaning quietly, little “uh, uh” noises each time my cock brushed against her spot, deep inside. She started making longer, louder noises, and her back tensed with pleasure. It drove me wild to watch her perfectly-proportioned ass bounce with each thrust. “Oh,” she whimpered quietly, “oh…!” I started moving faster; I could feel the cum rising again. Faster this time; I knew I’d pop off soon. “Oh baby,” she gasped, her face flushing. “Oh god yes, oh… fuck me baby,” she screwed her eyes shut tight and gripped my sheets. “I’m getting close,” I warned, one thumb moving down her crack. I started making little circles when I reached her asshole, putting just enough pressure for her to feel it- just like she’d instructed me, months before.
“Yeah, cum for me,” she gasped, looking over her shoulder at me; right in my face. Eye contact was something we rarely did. This was a service to me, after all. Education and therapy. Each time we did, though… it drove me wild. I leaned forward so my stomach was against her back, and she reached up and put one hand on the back of my head. “Oh, fuck me,” she said into my ear.
“I’m getting close,” I said again, my voice trembling. I could tell this one was going to be fucking intense.
“Baby,” she whispered. My heart skipped a beat. That whisper was rare. It always meant the same thing. I looked her in the eye, our faces inches apart. “Kiss me.” Our lips met with force, loud smacks echoing with each pull. “Oh baby,” she breathed into my mouth. “Oh baby, you wanna cum? You can cum for me.” I grunted with pleasure and primal instinct as my load built. “Cum for me.” She put the hand on the back of my head back down, and used her other hand to grab my cheek. “Cum inside me. I want to feel it. Come on.” I looked at her in the eye to make sure, and she nodded. “Blow it inside me baby. Get me pregnant.”
I had to choke back a scream as my semen burst out of my body like a bullet. Those three words, those three fucking words got me every time. My whole body convulsed as I orgasmed, and I could feel my dick pulsing like a living thing as it emptied itself inside of my sister. Her body reacted to it like a match to gasoline, clenching up like a fist as my cum splashed against her cervix.