Shiro gave birth to Yukie when she was 25. He was raised by a single woman, but Shiro continued to work part-time even after graduating from university, and did not show any sign of employment. Shiro had no femininity, and he had never even brought his friends with him. That should have been because Shiro had sexual feelings for his mother, Yukie. Yukie, who noticed it, invited Shiro to a hot spring trip to talk to her.
