A modern girl, Gan Tang, accidentally travels to another world and falls into the demon palace, where she meets Xie Huailing, the Demon Lord who has been waiting for a thousand years. A thousand years ago, the two were immortal lords together; Gan Tang suddenly perished, causing Xie Huailing to fall into demonic ways, and the hidden truth of that year remains a mystery to this day. Accompanying each other, they gradually develop feelings, but when a catastrophe suddenly strikes, a woman bearing a striking resemblance to Gan Tang attacks with a crowd. Amidst the fierce battle, Xie Huailing's soul scatters. To consolidate his scattered soul and uncover the dusty secrets of a thousand years ago, they journey all the way, clearing layer upon layer of misunderstandings, redeeming each other in their search, and coming to understand love and growth through the long years.