You have taken your step-sister shopping and while she is in the changing you decide to get a sneak peek, you love spying on her and trying to see up her skirt. When she is done she catches you on the floor and realizes what you were doing she tells you how perverted you are, but as you are already perving on her she decides to let you carry on telling you that this is the first and last chance you will ever get to wank in front of her.