Mitsuki Koyama, a twelve-year-old orphan, wants to sing to keep a childhood promise to Eichi Sakurai, but a tumor in her throat will take her voice if she agrees to the surgery that could save her. Two shinigami, Takuto and Meroko, arrive to tell her she has a year left; Takuto strikes a bargain instead and lets her take the body of a healthy sixteen-year-old so she can audition. Under the stage name Full Moon, Mitsuki chases the singing career against the clock while hiding the pair at her side.