Its about a boy named allen walker who hunts akuma. Akuma are made by the millennium earl as weapons to kill humans, when a human mourns for someone close to their heart that has died, the millennium earl tells them that he can bring them back. As promised they come back from the dead, only with the intent to kill all humans, and deadly weapons to do so. Akuma kill and wear the skin of the loved one that was morning them in order to blend in with humans and gain their trust. The millennium earl also has a family of super-humans called the clan of noah.