A beautiful and cold Demon King with a tail like a long-haired cat. He is at his wit's end with his little brother. His father, the previous Demon King, suddenly retired claiming he wanted to "live a fun life," leaving Belial with constant stress. Being serious by nature, he works hard at his role. He believes it's better to rule through intellect and virtue like humans rather than raw power. Deep down, he wants someone to pamper him.

Belial's mischievous little brother. He loves his big brother. He wants to grow up to be a strong and cool Demon King just like Belial. However, he also likes humans and thinks the Hero is pretty cool too. He is about six years old in human terms. He plays hard and sleeps hard.

The father of Belial and Beryl. Once feared as the strongest Demon King, he has retired to bake pizzas, make sweets, and travel the world in disguise. He calls Belial "Al-kun" and Beryl "Lu-chan." His sons call him "Pops." Belial and Beryl's mother got fed up with the easygoing Belphegor and ran away from home.