The story takes place in an originally peaceful world. At the beginning of the Air Era, the Celestial Army—the Great Bell Hall of the Temple—suddenly rose up, developed rapidly, and made hostile moves against humans.
Humanity begins to fight,
And formed the human legion to resist foreign enemies---the United States of Mankind,
The aliens were driven out of the human territory one by one,
At the same time,
The homeless tribes rise at the same time,
A new legion brought together by people of various alien races, a neutral faction between the Celestial Army and the United Nations of Humanity,
The neutral faction also includes the demons who always guard the Tower of Chaos.
This war,
In continental chronicles it is called,
"Chaos War"