15-year-old Ikeuchi Aya is an ordinary girl, the daughter of a family who works at a tofu shop, and a soon-to-be high schooler. However, odd things have been happening to Aya lately. She has been falling down often and walks strange. Her mother, Shioka, takes Aya to see the doctor, and he informs Shioka that Aya has spinocerebellar degeneration - a terrible disease where the cerebellum of the brain gradually deteriorates to the point where the victim cannot walk, speak, write, or eat.