In a desperate attempt to keep the peace over her imperial country Joseum, the Empress Consort Nanbakho Hanchae Hanuel-Ji settles for to unite her kingdom with the Gracemarin Empire led by Emperor George Winters IV by having her son, the 4th Prince Hanchae Kyung-Do enter a marriage with her cousin-in-law's niece Wilhelmina Riverwell.

Of course, things aren't so forthcoming in good spirits, especially when Kyung-Do does his best to avoid his childhood friend and cousin-in-law, even though he can't get the bigender noblewoman out of his heart and mind.

But what happens when the engaged couple give into their love for each other, while the country that surrounds them is threatened by the arrival of civil war between the ruling kingdom of Sanguem and the neighboring kingdom of Joneum, especially since Kyung-Do is already married to his other cousin Manbak Eun-Joo, who vies for the prince's love out of cunning jealousy?

And what happens when Wilhelmina's former betrothed, the 3rd Prince Sanaiya Yukimura from Touseiji, returns into her life once again only to be determined to reclaim his former bride?

And should Wilhelmina decide who owns his heart, what will happen should Joseum go to war with each other while Touseiji watches from afar?