Iruma Suzuki is a 14-year-old human boy who is sent to the netherworld when his selfish parents sell him to a demon named Sullivan. He is a cheerful and mild-natured boy who has a habit of being a pushover and unable to turn down an earnest request.

Sullivan asks Iruma to be his grandson and enrolls him in the Babyls Demon School, where he is placed in the Misfit class along with his classmates, Asmodeus Alice and Clara Valac. Terrified of being found out as a human and being eaten, Iruma must learn to adjust to his new life in the netherworld and blend in with his demon classmates at school.