Twelve-year-old Mitsuki Kouyama suffers from a throat sarcoma. Although this rare cancer can be cured by removing her vocal cords, Mitsuki refuses the treatment because she wants to become a pop singer and fulfill a childhood promise to Eichi Sakurai, her first love who moved to America. Unable to both recover and retain her voice, she lets her health decline, accepting her tragic fate. One day, while fleeing her music-disapproving grandmother's home to attend an audition, Mitsuki encounters two shinigami, Takuto Kira and Meroko Yui. Realizing Mitsuki can see them, Takuto and Meroko inform her that she has one year to live. Touched by her situation, Takuto grants Mitsuki the opportunity to chase her dream by giving her the power to transform into a healthy sixteen-year-old girl. After being selected for a contract with Seed Records, Mitsuki debuts under the stage name Full Moon and decides to pursue her music career before her life ends.