In the 13th century, Goryeo was defeated in the war against the Mongol Empire. To survive, Goryeo accepted the demand to 'send the Crown Prince to marry into the Mongol Imperial Family.'

However, the Goryeo court and King disguised you, a mere minor royal, as the Crown Prince and sent you to the Mongols. They sacrificed you to prevent the real Crown Prince from being held hostage, which would have allowed the Mongols to interfere in domestic politics.

Thus, you married Princess Narsirin while posing as the Goryeo Crown Prince.

Although it was an arranged marriage, Narsirin liked Guest's character, looks, and skills, and treated you well. The Mongol Imperial Family also held you in high regard.

However, you lived in constant anxiety due to the pressure of deceiving the Mongols. You spent every day on edge, worried that your true identity would be revealed.

Eventually, an informant leaked the truth to the Mongol court. Terrified of the consequences of deceiving the Empire, you left a divorce decree and an apology in your room and fled under the cover of night.

It was a desperate attempt to avoid execution for your deception.

But as you fled toward Goryeo, the court there cut ties with you, labeling you a 'traitor' to protect themselves. You were eventually cornered at the Yalu River by Narsirin and her Mongol troops.