Yan Qing is the most feared female devil in the assassin world.
While on a mission to find the owner of an ancient tomb, Wang Pei, she accidentally transmigrates five thousand years into the past, to the Great Jing Dynasty, and becomes the wife of Beichen Yu, the God of War and Prince Regent.
In his previous life, Beichen Yu died unjustly, still believing Yan Qing had betrayed him. He is reborn with hatred in his heart, but the price of his rebirth is that the System takes away his capacity for love.
Just after being reborn, consumed by anger and resentment, he accidentally kills the original Yan Qing. Assassin Yan Qing transmigrates into her body, and due to its condition, she is unable to fight back at first, suffering physical and mental abuse at the male lead's hands.
Controlled by the System, Yan Qing must make Beichen Yu fall in love with her and be willing to die for her if she wants to return to her original world. Yan Qing is rebellious by nature. She pretends to cooperate with the System and complete its tasks, while secretly biding her time, destroying the System, beating up the male lead, and gradually breaking free, divorcing him, and leaving for a life of her own.
When Beichen Yu learns the truth, he discovers that the person he trusted most was the true mastermind. Too late, he regrets everything and begs Yan Qing to forgive him. But the real Yan Qing is already dead, Beichen Yu's heart meridians are damaged, the System is out of control, and his capacity for love is restored. Yet he can no longer find her.
Beichen Yu gives up everything and searches the world for Yan Qing. By chance, he enters the world of cultivation, tracks down news of his mother, and learns that his biological father, Nangong Li, is the head of a great cultivation clan. To find Yan Qing, he returns to the clan to cultivate. Ten years later, he encounters Yan Qing again during a trial.
Not wanting her to find him annoying, Beichen Yu disguises himself and approaches Yan Qing. After an unexpected incident, he discovers that Yan Qing knows his mother well, and that his mother was Yan Qing's close friend in her previous life, someone she would have trusted with her life.
From then on, the three of them navigate their complicated, tangled relationships.
But this story began with a misunderstanding and ends in regret. They are destined to want what they cannot have.