In 4400 AD, a strange fog appeared on the earth. Within the range of the strange fog, corpse beasts would appear and bite humans at will. In order to fight against the corpse beasts, humans established the World Executor Organization. What is an executor? That is, the soldiers who perform the slaughter of corpse beasts are divided from top to bottom into special class, A class, B class, C class and D class. Corpse beasts are also divided into four levels ABCD. Among them, those who command corpse beasts above level A are called "elephant". Despite this, many areas have still fallen into disaster areas, and the total number of human beings is only one-third of what it was in 4400.
Concept: The distortion of human nature