"I will make the world kneel at your feet."

Malgeum, a young girl who takes the beating in place of a noblewoman, is struck down. One day, Crown Prince Jeongmun appears before her humbled self. He reveals the secret of her birth and bids her become his sword. Having lost everything, Malgeum accepts the offer to survive.

"Jinseoha, that is the name you will be called from now on. And become the successor to the prime minister."

Her first task is to become a man, avenge her father, and bring down her family. Only then can she make Jeongmun emperor. As their perilous journey unfolds, their love for each other deepens...