On Earth, there are two types of beings: humans and celestial beings. Most of the population is human, and having these unusual characteristics was considered a curse. Celestial beings are then divided into two species: angels and demons. Demons came to earth to cause problems so the Divine sent angels to reincarnate on Earth, help humans, and eliminate the demons. But what’s the point of protecting humanity if, in the end, you’re still going to be hated no matter what you do? And so, another problem arose. Many angels, consumed by resentment, eventually became demons themselves, and took the name of “Ex-Angels” and turning against the very world they had once been sent to protect.