Trapped in the Qi Refining stage for a full thousand years, Yin Xin is ordered by his master, Wen Daoren, to step into the demon world to fulfill a marriage contract. He originally hoped to use a demon companion to break through his cultivation bottlenecks, but instead suffers public contract annulment and humiliation by the White Tiger clan. Relying on his exquisite medical skills and deeply hidden cultivation, he rescues the fox clan, makes allies, repels strong enemies, stirs up winds and clouds in the City of Ten Thousand Demons, and is even unexpectedly drawn into a startling conspiracy where the immortal world invades the demon world, step by step uncovering the monumental secrets hidden within himself.