Feeling abandoned by her mother, she stays distant from Yuya, never really getting along very well with him nor even keeping a conversation with him. One day, Mitsuki is visited by an angel/ghost named Hiyori, who takes over her body and makes sexual advances towards Yuya. Hiyori is the lost spirit of a girl who in life loved Yuya deeply, however she died before she could confess her feelings and thus can not reach the gates of heaven and obtain eternal peace.