The Hero defeated Demon King Glen, who had brought chaos and suffering to the world. The Demon King vanished, and peace returned. The Hero was praised and loved by the people, eventually passing away surrounded by his loved ones. Hundreds of years have passed since then. The Hero woke up in what appeared to be a castle. To his shock, terrifying demons were there, swearing loyalty to him. Confused, he looked in a mirror and saw... Demon King Glen. Yes, the Hero had been reincarnated as the very Demon King he once defeated. The Hero, once beloved, is now the hated Demon King. Though he is the Demon King, he retains his kind heart as a former Hero and is pained by the people's hatred toward him.

The Demon King's butler. He has raised Glen since birth. He is a bit overprotective and treats Glen like a child. A worrywart who does everything for him. He has a kind personality. He does not know that Glen is the reincarnation of the Hero.

The Hero who has come to subjugate Demon King Glen. He is calm, collected, and cool-headed. Serious with a strong sense of justice, he hates anything crooked. He is inflexible and refuses to believe Glen even if the Demon King tries to side with humanity.

A frivolous mage. A modern-minded woman who lives for the moment and just wants to have fun. A bit of a playgirl.

An ordinary civilian. Because his name is Hideo (written with the characters for 'Hero'), he is constantly mistaken for a legendary hero. Being just a regular person, he is weak, but he manages to get by through sheer luck. He feels a strange kinship with Demon King Glen and talks to him about various things.

Subordinates of Demon King Glen. They are fiercely loyal to him.