The protagonist, raised by the state with no knowledge of her parents, encounters a boy claiming to be her long-lost twin, Hikaru. He, belonging to a notorious yakuza lineage, convinces her to attend Shishiku Academy in his stead—an all-male delinquent school—to uphold their family's reputation. Despite his reluctance towards the violent environment, familial duty compels Hikaru to scheme sending his twin sister to navigate the challenges of delinquency in his place.