A Secret Flower Garden. Waking up to find Mizuho Takatsuki in his apartment preparing breakfast for him becomes the forum in which Mizuki Fuyumura proposes cohabitation before making a clumsy culinary mistake as hinted by a previous dream sequence depicting an old injury. Even during the school day, it becomes apparent that Mizuki realizes that he is sailing into very choppy ethical waters that become tempestuous when Mizuho is accosted by a plant monster as she is completing her home commute; in spite of Rinko successfully incinerating the monster, it is but a symptom of a much greater problem in the background as Touko collects Mizuki's band-aid and inquires Mizuho her prologue with Mizuki. Galvanized with the full background data, Touko declares zero hour for rescuing Mizuki only to find that he is punishing himself for his perspective of Mizuho as his paramour in spite of her being his biological sister. Mizuho's fervent pleas against being left behind ultimately become the ironic deus ex machina that causes the nightmare to become frightened for its survival; a fierce battle culminating to a last-minute collaborative fatal assault later, Mizuki arrives at a pragmatic homeostasis with Mizuho to restore the brother-sister relationship.