Steamy Massage for Step Sister Ends with Me Fucking Her Bareback

My step-sister walks into my room after her shower wearing only a towel, asking me to give her a massage since her regular therapist cancelled. At first I'm hesitant, but she convinces me. She lies on her stomach on my bed and drops her towel slightly—I see her massive tits pressing against the mattress and get instantly hard. I start massaging her back while occasionally brushing against her huge breasts. She doesn't react at first. Then I pull her towel down lower and massage not just her back but her tits and ass too. Still no reaction from her. That's when I pull out my cock and start stroking it while touching her body. Moving on to her pussy, she finally asks what's happening—I tell her it's payment for the massage. She's not opposed, especially when I slide my dick into her mouth. We fuck in prone bone position, then she rolls onto her side as I finger-fuck her wet cunt while we make out and her massive tits bounce. We continue until I cum deep inside her pussy.