Azusa lives with her father and her younger brother, Ma-kun. One day, Ma-kun's friend comes to visit with a notice about an open school day that Ma-kun had thrown away. That night, when she asks Ma-kun about the situation, she finds out that he has become desperate, perhaps due to his inferiority complex about not having a mother. Worried about Ma-kun, Azusa decides to do something for her cute little brother.