Finding Full Moon (2002)

Twelve-year-old Mitsuki loves to sing and she dreams of becoming a famous singer to fulfill a promise she made to Eichi, a close friend who moved away to American two years previously. Unfortunatly, she suffers from a tumor in her throat which makes singing difficult for her. One day Takuto and Meroko, two shinigami (gods of death), suddenly appear and inform her that she will die in one year. With this in mind, Mitsuki becomes more determined than ever to realize her dreams of becoming a famous singer and to reunite with Eichi. Asking for help, Takuto transforms her into a 16 year old to aid Mitsuki in following her dreams in the one year she has left to live.