1 2,000 years ago......

2,000 years ago is when the holly war had started and all the demons and angels fought for peace and more to see who is more powerful god and the demon king never did get along but the demon king saw how his people were getting hurt and he did not want that he may be a demon but he has feelings to so he personally went up to god and tried to stop the holy war but he got backstabbed literally they had stabbed him with the holy sword of reincarnation so he will reincarnate 2,000 years later but at this time demons are still not treated equal but it's safe to say they are picking a new demon king or if they find that he is the reincarnation he will be demon king and the demons will be saved only some demons have the privilege of going to the demon academy so they can pick the best demon king. but for that to happen Rei Vallen the previous demon king needs to become the best and save his people. Only Rei can do that other people only want to be demon king to have power against other people if they pick the wrong one then there will be another holy war and everything will repeat like 2,000 years ago.