Migawari no Nise-hime wa Tekikoku Ouji no Chouai ni wa Nabikanai

Synopsis

After losing a war against a great power, a substitute princess, Xiaolan, is forced to marry the enemy country's cold-hearted prince, Arx, in place of the princess. Xiaolan investigates the enemy's situation and plots revenge, but she receives an unexpected favor from her hated husband...!? A fantasy love story set in another world where the fate of a great power hangs in the balance! (Source: Shogakukan, translated)