The modern city "Linzhou" is prosperous on the surface, but in fact it hides the dark situation of the coexistence of the "night tribe" (a group similar to vampires) and humans. The Night Clan survives by sucking human blood, and some high-level Night Clan can establish a symbiotic relationship with humans through "blood contracts" (humans gain some self-healing capabilities, and the Night Clan reduces their dependence on fresh blood)
