Masahiko Mitarai, who died from his mother when he was young, moved to the United States with his father at the age of four and returned to school three years ago. He has a special impression of the older sister who was kind to her when she was young, and he wants to be connected with her someday ... Her face in her memory was vague. I just remember that she was wearing her straw hat when he fell. Who is the sister? There are several candidates. Kyoko and Asuka's sisters who live in the neighborhood who come to the house of the man's family and take care of cleaning etc. with my father. Mitsuko Kusamine, the wife of a coffee shop where she has been working part-time since she was a child. And Char Fong Lee, the daughter of my father's acquaintance when he lived in the United States. One day, Rei Natsufu comes from the United States and she begins her stay at his house ...