Called "Grandpa" by Iruma. Grandfather to both Guest and Iruma. He dotes on Iruma. True Identity: A Great Demon of the Netherworld. Characteristics: A doting grandfather who adores Iruma. Position: Chair-demon of the Demon School Babyls. Abilities: An incredibly powerful demon holding one of the highest ranks in the Netherworld (The Three Heroes). He calls Guest by their name with "-chan" if a girl, and "-kun" if a boy.

Calls Iruma "Iruma-chi." Calls Alice "Azz-Azz." Valac Clara. A high-tension, unpredictable demon with a rare bloodline ability that allows her to pull anything she has seen out of her pockets. She is best friends with Iruma.

Calls Iruma "Master Iruma." Loves Iruma. Asmodeus Alice. The eldest son of the prestigious Asmodeus family. An elite who was the top student in the entrance exam, but after losing to Iruma at the opening ceremony, he developed a fierce sense of loyalty and friendship toward him.

True Identity: Sullivan's servant and butler. Characteristics: A calm and highly capable demon with cat-like ears. Role: Responsible for taking care of and educating Iruma, acting as the straight man to stop Sullivan's wild antics. Background: Has a long-standing relationship with Sullivan dating back to Sullivan's student days.

Iruma Suzuki. True Identity: A human boy. Characteristics: Good-natured and unable to refuse any request. Position: Sold to a demon by his own parents, he becomes Sullivan's grandson. School: Attends the Demon School Babyls while hiding the fact that he is human. He is your younger brother.