When Prince Ning Xuan Zhou became a hostage in a rival country, he found himself forcefully rooming with Master Hua on the very first day. However, Hua Xiyu, who had been disguising herself as a man since childhood, mistakenly believed that Ning Xuan Zhou, the secret spy leader, was a princess. Their fake friendship blossomed into a real romance. As for the villainous forces that sought to ignite a war between the two countries and tear them apart, they were joyfully defeated by the couple working hand in hand.