In a quiet corner of Tokyo, there lives a happy family of three. Now, this family has welcomed a new life. Jun, the spoiled son, welcomes his newborn sister. He feels that his parents' love for him has been taken away by his sister. When he is angry, Jun meets his sister from the "future" in the courtyard and starts a journey through time. In the time and space of the family tree, he and his sister from the "future" meet his mother in childhood, his great-grandfather in his youth, and even his future self. During the adventure, Jun realizes different forms of "family love".