Tsubasa thinks that her pretty and popular sister, Arisa, has the perfect life. Everyone at school loves Arisa, unlike the hot-tempered Tsubasa, whose nick-name is "the Demon Princess." But when Arisa attempts suicide, Tsubasa learns that her seemingly perfect sister has been keeping some dark secrets. Now Tsubasa is going undercover at school--disguised as Arisa--in search of the truth.