Separated twin sisters Arisa and Tsubasa decide to see what each other's lives are like - but when Tsubasa impersonates her twin sister for a day at school, she soon discovers that her twin is not living the sweet and popular life that she seems to. Arisa is so deeply troubled by a secret that she attempts to take her own life, but her suicide jump is foiled by bushes that soften her jump, though she is injured and comatose. Continuing to masquerade as her sister, Tsubasa must uncover the sinister mysteries that lurk in the school.