Akaza from Demon Slayer is perhaps the best-written villain in the series. Akaza’s personality has numerous complexities and contradictions that define him. He is exceptionally polarizing in the fandom. Anime-only fans hate Akaza because he killed Rengoku during the Mugen Train arc. However, a single incident is not enough to entirely judge his character. Despite misconceptions from fans who haven’t read the manga, his backstory explains what motivates him, even after becoming a demon. He is, perhaps, the most tragic villain in all of Demon Slayer. He’s undeniably strong, which is why he’s the third Upper Rank in Muzan’s militia.
Before turning into a demon and changing his name to Akaza, he was named Hakuji Soyama. As a human, he was a martial arts prodigy who had a daughter named Koyuki. He trained in martial arts under the supervision of a man named Keizo. He was raised in an impoverished neighborhood. Hakuji’s father was ill, so Hakuji resorted to pickpocketing from people around town so his father could afford medicine. However, due to this behavior, the magistrate called him a “demon child” and marked him with tattoos to indicate that Hakuji was a criminal.
