The story is set in the Tang dynasty, an era where humans co-exists alongside demons. A man who is of half-human and half-demon blood named Li Xuan broke the temporal peace of the world. The story follows Li Xuan as he deals with the responsibility of protecting his different bloodlines and the peace of Chang'an; as well as his complex relationship with Su Youlian, a spy from the demon tribe and Long Wei'er, his lover in a parallel world.