Tokiko Enomoto finds out that her husband Kazuya, who mostly lives at an apartment near his work while she and their children live at home, has been having an affair with a live-in mistress, Ryōko, at his apartment. Tokiko tells her two sons, Tarō and Jirō, that she has decided to divorce their father. The children are shocked but understand their mother's position. Kazuya realizes the damage he has done and tries to remedy the situation.
