Following his mother's death, high school student Kōsaku Sakamoto travels toTokyoto live with a friend of his mother's, Ibari Ōzora. When they arrive at the Ōzora household, Kōsaku discovers Ibari is the boss of the Ōzora Group yakuza organization. Kōsaku considers leaving, but has second thoughts when he meets Ibari's four children: Tsugumi, Tsubame, Hibari and Suzume. Although he initially believes Ibari to have four daughters, Kōsaku is shocked to learn that Hibari, who looks and behaves as a girl, wasassigned male at birth. The next day, Kōsaku enrolls into the same school as Hibari and Tsubame, and Kōsaku learns that everyone at school believes Hibari is a girl. Kōsaku is in the same class as Hibari, and one of their classmates named Makoto Shiina takes an instant dislike to Kōsaku. Shiina provokes Kōsaku and punches him only to get punched himself by Hibari moments later.