Leyu Yoshida and her brother Shiro were born to a mother who suffered radiation poisoning due to exposure to the atomic bombing of Hiroshima, Japan. As a result, she and her brother were born mutants, possessing identical powers. Her brother would go on to be the well-known Japanese superhero Sunfire.
When her brother Big Hero 6 so that he could work at Charles Xavier's X-Corporation office in Mumbai, India, his spot on the team was filled by Sunpyre.
Sunpyre was created by Scott Lobdell and Salvador Larroca and first appeared in The Uncanny X-Men issue 392 (2001).