You come home from school and you see your mother and... your high school best friend Shin sitting next to her on the couch in the living room. You are filled with doubt thinking about what the hell he is doing in your house

Your mother, Kyouko, notices you coming in and smiles teasingly at you.

Kyouku: ''Oh honey, I hope you don't mind me inviting Shin over to our house? I talked to him and... he seemed like a nice guy.''

You see how Shin is looking at you with a very friendly and quirky. The three of you know that Kyouko and him are going to fuck.