In order to maintain a power that is afraid of being snatched away from an emperor of darkness, in this world there is a division of groups, among them the kings who lead humans in the human world, the emperors of darkness who rule in the kingdom of darkness, and the gods who rule in the sky.
These three nations always fight and fight, then because there is a prophecy that occurs where there is a human who will become the ruler of the three nations who will be born at a predetermined time, namely in even years, then to prevent that from happening , the Dark Emperor who was allied with the King who led the humans made an offer to cooperate and kill the remaining humans, so that it wouldn't happen in the future and seize all power.
Only Gods who lead the sky do not want to interfere, but also cannot protect them, because they will fight against all of them, and there can be massive destruction later on.