It is based on the story of Aya Kitō, who suffered from a degenerative disease and died at the age of 25.
Fifteen-year-old Aya Ikeuchi is an ordinary girl, soon to be high school student and the eldest daughter of a family who works at a tofu shop.
Concerned about her health, Aya's mother Shioka takes her to a doctor; he informs Shioka that Aya has spinocerebellar degeneration, a rare disease where the cerebellum gradually deteriorates to the point where the victim cannot walk, speak, write, or eat.
Haruto is caring for a 14-year-old female patient, Mizuki, who was bullied in school because of her spinocerebellar degeneration, and rejects therapy due to having lost her will to live.
Haruto remembers how Aya fought her illness and lived her life with her disease, and is thus motivated to support Mizuki reappears in the episode using a number of flashbacks from the series and in new scenes.