When I was passing by my stepsister's room, I saw her lying on the bed in torn tight jeans, watching porn and masturbating. Her huge plump booty was peeping out of the hole so seductively, that I couldn't resist the temptation to touch it and rub her crotch. Since my step-sis felt horny as well, she willingly let me fuck her from behind and then straddled my boner to enjoy gonzo ride. In the end, I adorned her gorgeous plump buttocks with cum.