The Han Dynasty was defeated by Wuhuan and was forced to let Yixin marry Wuhuan.
At the wedding banquet, she did not marry the scheduled second prince, but married the third prince who had a strong interest in her. From then on, she began to have the experience of being both a teacher and a friend with the third prince.
The third prince was dissatisfied with many parts of his country. Yixin's arrival provided him with many novel concepts and theories, which allowed the third prince to formulate the preliminary appearance of the ideal country in his mind.
The third prince and Yixin continued to befriend each other, which attracted the attention of the Khan. Under the instigation of the second prince, he began to assassinate Yixin one by one. In the end, with the help of Yixin herself, the third prince, and the capable ministers around the third prince, one conspiracy after another was destroyed, forcing Khan to give up the assassination of Yixin.
In Wuhuan's war against the Han Dynasty, Khan unfortunately died. The eldest prince who was supposed to successfully inherit the throne was challenged by the second prince. Two princes compete for the throne, forcing the third prince to choose sides. The third prince was depressed and frustrated. He neither wanted his brothers to kill each other nor wanted to inherit the throne smoothly, but he was worried about the eldest prince's ability to govern.
The world was finally forced to be divided into three parts. The third prince gained a small piece of territory in grief, but he remembered the brotherhood, and finally regained his spirit and managed the territory well under Yixin's persuasion.
Under Yi Xin's suggestion, the third prince promoted the reform of the Han system, and the country's strength increased, which aroused the alarm of the eldest prince and the second prince. The two teamed up to attack the third prince, but were defeated with the cooperation of Yixin and the third prince, and were eventually forced to surrender their territory to the third prince.
The third prince unified the country and, with the help of Yixin, sent envoys to reestablish good relations with the Han Dynasty. Yixin was also sent back to her hometown and met her elderly parents. The former lover got married, so he made a private decision with the third prince to start a new life.
Purpose: The female protagonist helps the male protagonist to reform the Han Dynasty, and finally unifies the world and returns to his homeland.