Yukie gave birth to Shiro when she was 25 years old. She raised him alone, but even after graduating from university, Shiro continued to work part-time and showed no signs of getting a job. Shiro had no interest in women, and in fact he never brought his friends over. This was because Shiro had sexual feelings for his mother, Yukie. Yukie, who realized this, invited Shiro to a hot spring trip to have a heart-to-heart talk.