I thought you'd gone out.. I can't believe you just stood there silently watching me! How long would you have watched if I hadn't opened my eyes? Your slutty stepsister notices how hard you are from watching her, so you get your hard cock out and start stroking it for her.. turns out she loves that! She starts stroking herself too, and telling you to jerk off until she's begging for you to shoot your cum all over her while she orgasms!