Beet the Vandel Buster S01 E52 The Last Battle! Farewell, Black Horizon!!

The story takes place in a fantasy world where humans have been suffering from the attacks of the demon-like Vandels. Humans can fight back by becoming a Vandel Buster, a paid monster and Vandel assassin. The protagonist of the story, Beet, is a young boy who becomes a Vandel Buster to be like his heroes, the Zenon Warriors.