Twelve-year-old Kamiyama Mantsuki (voiced by Ogata Megumi) lives with her grandmother. She loves singing, but her grandmother strictly forbids her from singing because of throat cancer. Mantsuki has a promise with her childhood playmate Eichi (voiced by Kimura Ryohei). In order to fulfill the promise, Mantsuki strives to become a singer. One day, a group called "Chive Ramen" appeared in front of Mantsuki. They called themselves apprentice death gods Takuto (voiced by Saito Kyoo) and Yui (voiced by Honda Chieko). They told Mantsuki that she only had one year left to live, and as long as she got her soul, Takuto could become a formal death god. The sad Mantsuki moved Yui, and they decided to help Mantsuki fulfill her last wish before she died. Yui changed Mantsuki's appearance into a sixteen-year-old girl so that she would be eligible to participate in the singing competition. Unexpectedly, Mantsuki became successful with the stage name "FULLMOON", and in the process, Takuto's feelings for Mantsuki gradually became complicated. Takuto is devastated by Eichi's return, and his long-lost memories are the key to threatening his survival.