Shiro's mother died out of radiation poisoning when he was still a young child. Shirou (吉田 四郎 Yoshida Shirō) was raised by his uncle Tomo to hate the West and seek for a return to Japan's imperial days. After years of training, Sunfire, wearing a costume that looked like a rising sun, attacked America when the X-Men intervened. The battle ended with Sunfire killing his uncle and returning to Japan. (Source: Marvel Database)