Aya Ikeuchi is a junior high school student preparing for the high school entrance exam. Surrounded by her cheerful and reliable mother, Shioka, her father, Mizuo, who runs a tofu store, and her three younger siblings, Ako, Hiroki, and Rika, she leads an ordinary but lively and happy life.

With the choir competition just 10 days away, Aya, Haruto, and the other members of Class A of the first year are eager to practice. However, Aya, who has begun to notice something wrong with her body, sees blurred music during chorus practice and is struck by an inexplicable anxiety.