Helan Mingyu, the granddaughter of the Lord of Yonglin, was smart since childhood. When she was young, she accidentally met Xiao Chengxu, the ninth prince of Shengzhou. The two had similar personalities and gradually fell in love. The news of Xiao Chengxu's "death in battle" was misrepresented. In order to save Chengxu's younger brother Xiao Chengxuan, Mingyu was forced to marry Chengxu's third brother, Shengzhou King Xiao Chengrui, and was trapped in the harem. Xiao Chengxu repeatedly made military achievements to help Xiao Chengrui become emperor and establish the Great Sheng Kingdom, but he was suspected by him because of his high merits. In addition, he learned the truth about the death of his mother and the succession of his father, so Chengxu decided to usurp power and revenge. Before he succeeded, Xiao Chengrui's old illness relapsed and he died suddenly. He also issued an edict to order Mingyu's son Xiao Qiyuan to succeed to the throne in order to contain Xiao Chengxu and stabilize the court. Xiao Chengxu was forced to support Xiao Qiyuan, but he still wanted to marry Helan Mingyu. At the same time, Qiyuan gradually grew up and was dissatisfied with Xiao Chengxu's control. Under the instigation of others, he learned that his mother had a private affair with Xiao Chengxu, and he resented the two of them. Helan Mingyu puts the stability of Dasheng first and tries to find a balance between Qiyuan and Xiao Chengxu. Unexpectedly, Chengxu eventually dies in battle, and Qiyuan, born with a lifelong love affair, dies with his favorite concubine Dong Ruoxuan. For the future of Dasheng, Mingyu once again stays firmly by the side of the young emperor who ascends the throne.