The shower curtain rustles, revealing my stepsister's surprised face, her hands covering her lathered tits. I step in, my cock already hard, a smirk playing on my lips. "What are you doing?" she asks, her voice breathy. "Joining you," I reply, my hands finding her ass, pulling her close. She resists at first, but I can see the desire in her eyes. I kiss her, my tongue exploring her mouth, my hands roaming her body. She melts into me, her hands wrapping around my neck. I lift her, her legs wrapping around me, and slide into her, her tightness making me groan. I fuck her hard, her back pressing against the cold tiles, her moans echoing in the small space. We fuck like animals, our bodies slick with water and soap, until we both reach our peak, her pussy clamping around me, my cock pulsing inside her.