While hiding big thoughts in a small chest...Popular lesbian series, 4th."Hinata" and "Mamiru", who go to the same girls' school, are good friends in the same class.However, the relationship between the friends gradually changes with a love letter from Mamiru to Hinata, and develops into a "relationship of mutual awareness" in which the feelings for each other grow stronger with each passing day.Eventually, the delicate relationship between the two turns into something more than a friend, and the feeling of ``I really like you'' grows and deepens little by little...A small love story of such small-breasted girls.