Yukina single-handedly raised her son, Masaaki, until he graduated from university, and successfully found a job. Masaaki started living alone when he got a job, and Yukina also ended up living alone. On the day Yukina celebrates her 50th birthday, Masaaki invites her to a hot spring trip as a birthday present. Yukina gets excited when she sees Masaaki's body for the first time in a while while traveling. Masaaki also had an erection when he saw his mother's underwear. The destination of such two people is...
