Shiro Yoshida grew up with a huge resentment against the United States. His mother was exposed to the radiation of the atomic bomb at Hiroshima and she died during his birth. His dad, a member of the Japanese Clan Yashida, became a diplomat to the United Nations and Shiro was pretty much raised by his uncle.
Shiro’s uncle Tomo took him to a site in Hiroshima, and got him to touch the ground. There, the radioactive soil somehow triggered his mutation. Shiro trained for months before he was able to control his flame fully. His uncle Tomo was purely anti-America. He instilled his hatred upon Shiro and is responsible for giving him his costume and codename of Sunfire.
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