She died a tragic death in her previous life, and all she wanted to know was why he hated her so much...
They were in love, and everything should have ended happily. Instead, she died in an assassination he had carefully planned...
Her death left him yearning for her for an entire lifetime. Only after being reborn did he realize she was the woman he had searched for all his life, the one he loved most. In this life, he devoted everything to cherishing her, making amends for the pain he had caused her in their previous life.
After being reborn, she wanted to leave him. But they had been married by imperial decree, and divorce was no simple matter. For many reasons, she chose to stay for the time being. Under his devoted care, she finally chose to forgive him.
He simply hadn't recognized her. He misunderstood her for an entire lifetime, and spent that lifetime yearning for her.