People are always afraid of the unknown, of things they cannot see or touch, like "ghosts." Even so, some will loudly discuss with their friends, "How could ghosts possibly exist in this world?" They wouldn't say that if they ever encountered one. For example, Chen Yi ran into a supernatural incident during a graduation trip with his classmates, and he was the only one who survived. Ever since, he has been fighting ghosts. If anyone told him ghosts didn't exist, he would surely laugh and say, "I've spent three years fighting ghosts, and you say there were never any ghosts in this world?"
The background story is pretty good, but it's too tiring to watch. It's either fighting or on the way to fight.