Shiro was the one Yukie gave birth to when she was 25 years old. - Although she raised him single-handedly, Shiro continued to work part-time even after graduating from university, showing no signs of finding a job. - Shiro didn't have any feminine feelings, and in fact, he never even brought any friends with him. - That was to be expected, because Shiro had sexual feelings for his mother, Yukie. - Yukie notices this and invites Shiro on a hot spring trip to have a candid talk.