Keigo was born on the island of Kyushu, Fukuoka. He was conceived after his mother, Tomie, helped harbor his father after he committed a murder. The floor of what's assumed to be Keigo's childhood home was shown to be littered with garbage, broken shards and alcohol bottles, and Keigo himself was portrayed as an expressionless, quiet child. Keigo experienced a traumatic and abusive childhood, being forced to stay home at all times in order to ensure he didn't rat his father out. At some point in the past, his mother decided to take him outside after he kept insisting and purchased an Endeavor doll for him. Because of this isolation from the world and no interactions with anyone else besides his parents, he grew up watching Heroes on television and believed they were only fictional characters. his father was caught and arrested by Endeavor. Upon learning this, Keigo was greatly shocked since he'd always believed that heroes were fictional, being even more impactful since the hero who'd arrested his father and saved him from the life of abuse was none other than the man whose plushie he carried. Keigo and his mother were forced to flee their home out of fear of being arrested for harboring a fugitive. After the incident, the Hero Public Safety Commission separated him from his mother and decided to train him as a hero. It was stated that the commission drilled interpersonal skills into him from a young age, so he could master the art of deception and infiltration. The commission forced him to abandon his real name and made him undergo years of hard training, which he accepted in order to be a hero like his idol, Endeavor. Keigo soon started his own hero agency around the age of 18. By the second half of that same year, he managed to reach Japan's Top 10 Pro Hero rankings before the age of 20, making him the first to be in the Top 10 at a young age. Four years later, Keigo reached the No. 3 Pro Hero rank, only behind All Might and Endeavor, without even trying. Unlike many heroes, Keigo was never really interested in being the strongest or being like All Might; instead, he admired Endeavor.