Ikeuchi Aya is an ordinary 15 year-old girl and soon-to-be high school student. However, odd things start to afflict Aya. She begins to fall down frequently and walk awkwardly. With sincere concern, Aya's mother takes her to the doctor only to be informed that Aya has been diagnosed with Spinocerebellar Degeneration, a disease that deteriorates the brain to the point of death.