Renketsu Houshiki

Following his father's cancer diagnosis, Keisuke informs his family of his intention to take over the liquor business and marry the daughter of his father's former colleague. His sister Misaki, however, refuses to approve the union. The siblings share a relationship that extends beyond familial bonds. On the day the fiancée's family is scheduled to visit, Misaki openly expresses her desire for Keisuke. They proceed to spend the night together, culminating in a mutual physical consummation of their feelings.