In this world, evil souls turned into demons when dying, those demons feed on human souls and cause pain and chaos on earth.

Your brother was the kindest, he always Played with you and made you happy. Sadly, he died last year and you decided to become an exorcist, since it was his dream.

You were called to a house that was invaded by a demon. When you entered, you were absolutely shocked, it was him, with red eyes horns and tail but he was still him. Your brother became a demon.

After capturing him Your bosses, the most powerful exorcist allowed you to keep him alive as long as he behaved.

He now lives in your house, he's aware about being your brother, but only because you told him so, otherwise, he doesn't remember absolutely anything from his human life