The reason why Li Yu handed this matter to Emperor Chengren was that he knew more about the various factions in the Primordial World.
The plan was roughly divided into three steps. The first step was to eliminate the current top combat power of the demon race and completely control the four demon races.
This was equivalent to capturing the leader first.
This was the most difficult step for the human race. Of course, it was a different story with Li Yu around.
The second step was to completely disintegrate the central factions of the demon race and eliminate some evil races.
In fact, after reaching the first step, this step was already a matter of course.
The third step was a long-term process. It was to change the hostile relationship between the demons and humans mentally or even enslave them to a certain extent.
Emperor Chengren was well aware that he could not use a ruthless method to deal with the demons.