Wu Xin is an immortal being with no memory of his past, wandering through the world for centuries. He possesses supernatural abilities and sustains himself by hunting demons and spirits that plague the mortal realm. Despite his powers, he lives a life of poverty and simplicity, often finding himself entangled in the complex lives of humans during the turbulent early Republican era of China. As he travels, he encounters a spirited young woman named Li Yueya, who becomes his companion and moral anchor. Together, they face various malevolent entities, including the powerful and vengeful spirit Yue Qiluo. The series explores themes of love, sacrifice, and the burden of immortality as Wu Xin struggles to protect those he cares about while uncovering the mysteries of his own eternal existence.