GS-217 - I went to my friend's house and his sister was working out in a leotard

I went to my friend's house and he wasn't there, so I waited. Then his sister appeared, working out in a leotard! She noticed me and started showing off her body. She rubbed her butt against my face and crotch, which got me rock hard. She couldn't resist anymore and demanded it, so we went at it.