Kaioh (界王, Kai-O) is the single strongest most powerful hero in the A Villain For Fun universe, After becoming villainous, he titles himself as The Messiah (救世主, Kyuseishu) upon acquiring the furthest depths of his potential and developing his power to the limit. He plays the role of a major antagonistic presence in the series, who embodies many of the characteristics which the protagonist nagoya detests and despises in a hero.