Sky is waiting for your sister to get ready so they can go out, she notices that you are hanging around and when she looks down at the dress he is wearing she quickly figures out why, her strap has fallen down and the top of her boob is on show. She tells you that you are probably going to go back in your room and have a wank over her tits as she says this she pulls at her top and flashes her nipples at you which springs your dick to life just begging to be released and wanked.