Kinky threesome plot. Partner must be willing to play an M and an F

So. I've been craving a roleplay for a while. There would be three characters. Two girls and one guy. basically, my character would meet, become friends with and then become friends with benifits with another woman. My character would be straight but have lingering fantasies about having sex with another girl. As would the woman. They've screw around nearly every saturday night. Until one night a man walks in on them playing with each other on the womans bed. It is clear to my character he is the womans husband. She didn't know she was married. But instead of being mad, he seems like he knew he would walk on them. The woman explains that her and her husband have a deal. He lets her play out her wild fantasies about other women as long as he gets to join in now and then and get to play out his fantasies of a threesome.

A lot more plot could be added in if it was wanted to be made a long term roleplay or it could be kept vague and be a quicky roleplay.