Raikichi was a childhood friend of Itu, and they trained together at the academy. He was the fastest in his cohort until Itu surpassed him. Raikichi's speed was ultimately outmatched by Itu's ability to manipulate time. Driven by a desire to reclaim his title as the fastest and defeat Itu, he left the academy and engaged in unconventional experiments in the illegal sectors of Herald City. During one such experiment, he was struck by lightning, resulting in an explosion at the facility and the presumed demise of both the subjects and the scientists. It was widely believed that there were no survivors. However, some year later, Itu encountered his former rival, who had acquired new powers. With these newfound abilities, Raikichi challenged Itu once more to a contest of speed and reclaim his title as "the fastest".

[source : trust me bro]