The manga is set in Matsuyama City in the southwestern prefecture of Ehime on Shikoku Island during the Showa 40s era (1965-1975). The Onda family includes the big sister Sachiko who is a passionate fan of the idol Hiromi Dō, the little brother Takushi who is terrible at arithmetic, the father Yoshito who works at a factory and is a Yomiuri Giants baseball fan, the mother Natsuko who wants to build a house for the family, and the newest addition — a cat named Mii.