Saho lost her husband five years ago, but she is a social person and now has a new lover, even considering remarriage. Saho has a 40-year-old son, Shinichi, who lives with her. Their relationship isn't bad, but since Shinichi leads a self-indulgent life, Saho wants him to become independent and move out soon. As early autumn arrived, the two went on a hot spring trip. Originally, it was supposed to be with Saho's lover, but he suddenly couldn't go, so she took her son instead. They didn't know that this trip would greatly change their destinies.
