Because humans continue to commit suicide, the population of the underworld occupies an increasingly smaller area. That is to say, the passage between the underworld and the human world is getting weaker and weaker because of the frequent reception of souls of the dead. This makes some demons and ghosts who cannot bear loneliness have the idea of going to the human world. In this way, the miserable candidate Xiao Wuchang begins his life of tutoring in name but actually transferring souls and catching monsters.