High school student, Yo, lived with her father, Nao, after her mother, Sachiyo, left the family when she was very young. However, their life together came to an end and they started a new life as a family of four with her father's second marriage partner, Miko, and her stepdaughter, four-year-old Hinata. She confides in Riku, who belongs to the same art club as Yo, about her confusion about this new life. Yo, who has been developing curiosity for her biological mother, Sachiyo, promises to go with Riku to Sachiyo's art exhibition.