Helping My Girlfriend’s Mom Stretch: Yoga Threesome

I didn’t know my girlfriend’s stepmom was such a freak! She’d been eyeing me for a while, so I figured maybe she thinks I’m cute or sweet or whatever, but what I was about to find out was way, way more perverted. She invited me over during a yoga session, and was really playing it up. She wanted help stretching out, getting as open as possible. Next thing I know, she’s encouraging my girlfriend and me to fuck around with her right then and there! Whoa! Would it really be okay to do something like this? Fuck it! Moral questions can wait until after I’ve gotten my dick wet…