Humanoid Monster Bem (2006)

Overview

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.

Source: AniList