Kazunari Katsuki (Gaku Sano) lied to his classmate that Tokyo stinks. Because of his comment, he goes to Tokyo alone. On his way back, he misses his flight back to Kumamoto. Kazunari only 3,400 yen in his pocket. He becomes confused about his missed flight. At that time, Masami Tanaka (Kaoru Sugita), who works at an airport souvenir shop, talks to Kazunari. On Kazunari's unusual trip back to Kumamoto, he meets many different adults and begins to think about his life.
The year is Seitoku 2 (1712), and Japan has a new ruler. But Ietsugu, the 7th Tokugawa shogun, is only four years old. The power vacuum this creates has Edo Castle roiling in political intrigue and personal positioning of all kinds.
Researcher Mutsugoro takes his family to a remote and uninhabited island near Hokkaido, to study the local population of wild bears. Nearby poachers make his life difficult, and he "inherits" an orphaned bear cub, whom the family call Donbe and raise as one of their own.
