Bem, Bela, and Belo are not "monsters," nor "humans," but "humanoid monsters." They usually disguise themselves as a human family living together, but their appearances transform into ugly monsters when their emotions become uncontrollable due to intense anger or extreme sorrow. Even if they save humans out of a sense of justice, they are feared and hated by humans just because they are humanoid monsters. They have lived in this manner for centuries, and their only wish is to become humans as soon as possible. One night, Bem saves a man, and becomes friends with detective Natsume. At Natsume's house, he finds a photo of a man who may hold a clue as to how to become humans. They go to meet the man, Ogata, who denies any knowledge and disappoints them. Meanwhile, the case of the man Bem had saved, rapidly unfolds, and Natsume finds himself in trouble. Can Bem save Natsume?! Will Bem and his sidekicks' dream come true?!