Segawa Yuta is a freshman of a university. He lost his parents when he was small and was raised by his sister Yuri. Yuta has been living alone since Yuri got married to a middle aged man when Yuta was a junior high student. One day, Yuri visited Yuta's apartment and asked him to take care of her three daughters while Yuri and her husband were on a trip. He unwillingly accepted the job but the plane Yuri took went down in a plane crash. In order to prevent the daughters from being adopted separately by relatives, Yuta decided to take in all three girls. A life of a strange family in a tiny apartment begins.