Domestic na Kanojo

Insanely in love with his teacher Hina, Natsuo Fujii. He accepts a mixer in an effort to move on. Rui Tachibana, a strange female he meets there, asks him to leave incognito. She brings him to her home and invites him to have sex. Natsuo loses his virginity to her since he is disappointed that his love will not result in anything. The following day, Natsuo's father informs him that he wants to remarry and that his potential spouse will visit their home that evening. When the door opens, it is revealed that Rui is Hina's younger sister and that both of them are the daughters of Tsukiko Tachibana, the woman his father desires to wed.