The fairy world and the demon world are two different worlds. The rules restrict the people in the fairy and demon worlds from going out or going to the human world without permission. Until one day, the power of the rules loosens, the fairy and demon worlds are in chaos, and the human world is in ruins...
The reason why the rules are loosened is known only to a few people who have a glimpse of the way of heaven.
Purpose: To safeguard justice in the world.