Shiro, the son of Yukie, was born when she was 25 years old. Since childhood, Shiro has harbored deep affection for his mother Yukie, who raised him alone. Even as he grew older, he showed no signs of securing stable employment, continuously working part-time jobs. He was quiet and rarely socialized with friends. The reason became clear when he realized his feelings for his mother Yukie were of a sexual nature. Yukie noticed his emotions and invited him on a hot spring trip, hoping to open his heart and have an honest conversation.