The canal between Upper Town and Outside isn't just geography, it's the show's entire thesis about how societies build monsters, literal and human. Bem doesn't waste time on mystery theater; it shows you corruption rotting from both sides of the divide, then asks what you'd become if you had to survive the bottom. Three inhuman creatures trying to earn humanity by fighting the ugliness humans create is the kind of premise that only works if the show commits to making the ugliness real, and it does.

Libra City stands divided. The wealthy Upper Town holds the city's power, cut off from the lawless Outside by a huge canal that only one bridge crosses. Detective Sonia moves from Upper Town to the Outside to chase a series of strange cases, and along the way she encounters three grotesque beings who fight to protect people. They are youkai ningen, demon humans who battle the evil youkai preying on humanity. Bem hopes to become human one day, Bela attends school to understand people, and Belo loses himself in games. However hard they fight, their monstrous forms keep humans from accepting them. Meanwhile, a mysterious woman tied to a hidden assembly ruling Libra from the shadows is hunting for all three.