Fucking stepsis before a rave

I caught my stepsis planning to sneak out of the house to a rave in the skimpiest outfit ever. Now this skinny bitch owes me a big-time favor and I want her to take care of my cock with her lips and pussy. She will do anything to have me let her go out tonight, even let me fuck her and cum in her mouth. Damn, if I knew my stepsister had such a tight perfectly fuckable pussy and loved to fuck from behind, we'd be doing it long time ago.