Growing up without any family, the protagonist had no idea who her parents were and spent her formative years in state care. One day, however, her twin brother, Hikaru, appeared in her life with a brash and daring appeal: "Could you go to school for me?" But there was a catch, the school he had in mind was a school for troubled delinquent boys, and it made her uneasy. Hikaru's family, the Onigashima, was notorious in the criminal world, and he had to attend the Shishiku Academy to gain control over the unruly students there. Although frightened, Hikaru's respect for tradition meant that he could not refuse to attend the delinquent school. When he discovered that his twin sister was still alive, he saw an opportunity to avoid his fate and made the decision to send her instead.
