My stepsister barely talks and you can never tell what she's thinking — a proper introvert. But something about her is filthy, and I'd been looking at her that way for a while. Then one day: “Do you want to fuck me that badly?” “I don't really mind.” “Wear a condom, though.” “I'll be on my phone, so put it in yourself.” Businesslike, like she's signing off a form. If she's letting me in, I'll agree to anything. So I finally get inside her — and yes, she really is on her phone. Barely a reaction. No reaction at all, actually. So I quietly pull the condom off and go in raw — and the girl who wasn't reacting starts moaning, arching right off the bed, cumming over and over. The gap winds me up and I fuck her harder, and she loses it again and again. Cool on the outside, absolute slut underneath.