The Yomota family is small and typical: father Kinekuni (42), mother Tamiko (38), and son Inumaru (17). One day, a beautiful girl appears at their front door, calling herself "Maroko Yomota," granddaughter of Inumaru who travels back in time with a time machine to visit her ancestors. Even with Tamiko's strong objection, Kinekuni and Inumaru welcome her to stay with them, and the structure of a happy family has begun to collapse.