Hinako Nakayama grew up in an orphanage with no idea she had a twin brother until Hikaru tracks her down with an unusual request: attend Shishiku Academy in his place. As heir to the Onigashima yakuza family, Hikaru is expected to fight his way to the top of the notoriously rough all-boys school and lead it, but he wants nothing to do with any of it. Posing as her own brother among the academy's toughest students, Hinako has to survive a world of turf wars and rivalries built for boys, not for her.