Modern cities are suddenly faced with the advent of the "gloomy era". Invisible and insubstantial ghosts and ghosts that distort space quietly breed. They act according to their own weird and cruel "rules" and cannot be physically eliminated. They can only fight by understanding the rules, exploiting the conflicts between the rules, or accommodating their core fragments. Human civilization is struggling in despair, and the hastily established "Folklore Anomaly Investigation Bureau" has become an apparent line of defense. However, deeper clues point to ancient legends: these rules of ghosts seem to be inextricably linked to the concept of "eighteen levels of hell". Each level of hell is not a space, but a projection and pollution of the "original sin rule" or "extreme pain mode" in the real world. Fragments of older, forgotten "mythical" authority are scattered among them, becoming a twisted source of power in despair.
