This guy moved to Tokyo to start a business but all failed and he just returned to his Brother’s house with just a pile of debts. The Brother is pissed off and wants to kick him out. And this guy also resents back the Brother, because he married the girl he liked: Tsumugi Akari.
He feels very pathetic, and with Akari being very kind to him, the attraction is increasing. In a sexual way.
All the pressure ends up venting in an explosion of sex and r*pe, where he fulfills all his fantasies.