One couple throughout the early arc + palace intrigue + angst + body-swap in the middle + woman tortures man + powerful female lead in the later arc
She is a princess of the former dynasty. He is the crown prince of an enemy nation, disguised as a prince.
“Gu Nanxuan, may we never meet again, in life or death.” Ye Li used the last of her strength to force out the words.
After returning in another body, she is determined to take his place. She'll avenge her country and family, and the betrayal she suffered!
He merely gave a cold laugh. “You can't die. If you do, I'll be heartbroken.”
(Please don't try to understand the author's state of mind.)