Yuuta's sister Yuri finally entrusts her daughters to him as she and her husband Shingo leaves for a business trip-cum-honeymoon, with an instruction never to bring his girlfriend into the house. Coming home after seeing the couple off at the airport, Sora and Miu then introduce him to the house rules. Everything goes smoothly for the rest of the day well into bedtime until news came that the plane Yuri and Shingo were in crashed and they were among those considered missing. The family decides to break the siblings up, but Yuuta, remembering how his sister raised him herself after being orphaned, decides to take them all with him in his apartment.
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 missing. 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.
