The movie is based on Umimachi Diary which was written by Akimi Yoshida. The main plot of this movie is that there are three sisters: 29-year-old Sachi Kouda, 22-year-old Yoshino Kouda, and 19-year-old Chika Kouda. All of them live together in the house of their grandparents in Kamakura and their parents left them after they grow up. One day they hear the news of the death of their father after 15 years and they go to the funeral and there they meet their 14-year-old sisters Suzu Asano. There was no one to take care of her, so they invited her to live with them.