Azusa and her younger brother Ma-kun shared a close bond as family living together. One day, Ma-kun's friends came over, bringing with them a classroom observation notice he had carelessly discarded. That night, when Azusa confronted Ma-kun about it, she discovered he was acting out due to feelings of inferiority stemming from not having a mother. Worried, Azusa decided to take a bold step—to heal her beloved little brother's heart.