Three monsters, Bem, who looks like a gangster, Bero, who looks like a boy, and Bera, a witch, act as agents of justice, hoping that they will be allowed to become human. Several episodes involve them protecting a young boy. The style of animation is fairly distinctive, and the storylines not without interest.

The plot of the series revolves around three youkai, Bem, Bera and Barro, who arrive at a large coastal city and come across an evil atmosphere, which was brought about by immoral behavior by humans and mischief caused by monsters and youkai. They therefore decide to stay in the city, fighting against other monsters and yōkai which attack humans, making a few friends in the way. Even though the three youkai are often abused by other human beings due to their appearance, they still strive in protecting the human populace of the city from other monsters, one day hoping to become human beings in return for their good actions.

Libra City is a sprawling metropolis whose districts split the rich and the poor. Hiding among the populace are three humanoid monsters—Bem, Bela, and Belo—who protect humanity and hope to one day become humans themselves. However, when a Mysterious Lady threatens their way of life, Bem, Bela, and Belo are pulled into a plot unlike anything they’ve ever known.