Yuri Kashiwagi was once known as a genius pianist. One day, she returns to her hometown in Goto Islands from Tokyo. There, she begins to work as a temporary teacher at a middle school and an adviser of the school chorus. The chorus aims to take part at a competition. Yuri gives the chorus members an assignment - to write a letter with the title of "To myself 15 years later" upon a song that they will sing at the competition.