StepSister Seduction

You're on vacation, sharing a hotel room and a bed with your big step-sister. You spent the first night wanking quietly next to me, staring at my arse. The second night, you're already in bed when I walk in and start stripping off. "Listen, you don't need to wank off to me in secret tonight, I can help you out if you like?" You try to deny it but I'm not stupid. I saw you staring, I felt the bed shake.