My Dear Stepbrother helped with math and cum in my tight ass

The kitchen light flickered above, casting long, dancing shadows over the marble countertop as I sat there, a textbook spread out in front of me, totally lost in calculus. My stepbrother, Jake, walked in, catching me staring at the messy equations, my brain fried. He leaned over, his breath hot on my neck, whispering, “Need some help with those numbers, sis?” I felt his hand slide up my thigh, under my skirt. His fingers teased the edge of my panties, tracing the lace. I squirmed, trying to focus on the math, but all I could feel was his touch, his heat. He slipped a finger inside, then another, pumping slowly, rhythmically, as if solving some dirty equation of his own. I moaned softly, my head falling back, eyes closed. He leaned in, his lips brushing my ear, “You like that, don’t you? Your tight little cunt clenching around my fingers.” He pulled them out, sucking them clean, his eyes never leaving mine. I was soaked, my pussy throbbing, aching for more. He spun me around, bent me over the counter, my ass in the air. He yanked down my panties, his hand smacking my bare cheek. I yelped, then pushed back, wanting more. He spat on my asshole, rubbing his thumb in slow, dirty circles. I groaned, my face pressed against the cold marble, as he lined up behind me, his cock hard and ready. He pressed against my tight ass, pushing in slowly, inch by inch, until he was fully sheathed inside me. I cried out, the pain mixing with pleasure, as he began to fuck me, hard and deep, his hips slapping against my ass. He reached around, his fingers finding my clit, rubbing it in time with his thrusts. I was a mess, my body shaking, my breath coming in ragged gasps. He leaned over me, his voice a low growl, “That’s it, sis. Take my cock. Take every inch of it.” I did, my body convulsing as I came, hard and dirty, my ass clenching around his cock. He groaned, his hips jerking, as he filled my ass with his hot cum, his body shaking with his release. We stayed like that for a moment, our bodies slick with sweat, our breaths ragged, before he pulled out, leaving me empty and spent. He smacked my ass one last time, a dirty grin on his face, as he walked away, leaving me to clean up the mess he’d made.