One weekend, Kenichi goes out with his mother, leaving his father Toshio behind. However, his mother has made a mistake with her plans and is due to return home soon after. Kenichi and his mother see Toshio bringing his young mistress, Tsubaki, into their home. Shocked, his mother returns to her parents' home, and when Kenichi confronts Toshio, he tries to avoid seeing Tsubaki. Tsubaki, unable to accept this, suddenly shows up at the house to greet Kenichi, and takes out her anger on him.