In Qingming City, where the boundaries between humans and monsters are gradually blurring, young Xiao Diyun accidentally inherited a incomplete "Hundred Demons Book" and was involved in a series of bizarre events. The old locust trees in the city cry in the middle of the night, strange faces are reflected in the mirror, and the boatmen crossing the river are entangled by water monsters... Those monsters that only exist in legends are intruding into the world in various forms.
Xiao Diyun discovered that behind every monster there is an unknown past, whether it is obsession, regret, or inextricable ties with humans. He teamed up with the mysterious demon hunter Su Wan and Han Shuishengxin, a girl who can understand demon language, to explore the secrets of the "Hundred Demon Spectrum" and find balance in the dispute between humans and demons.
However, as the investigation deepens, a conspiracy related to the survival of the two worlds gradually emerges - the truth of the human-monster war a hundred years ago has been covered up, a sleeping ancient existence is about to awaken, and Shen Yan seems to have a destiny that even he himself does not know...
