My Crown Prince Is a Daughter

Prince Su Jin of Dayin is actually a woman. After the Virtuous King poisons the Emperor with a child-killing drug, the Emperor forces Su Jin to dress as a man to stabilize the throne. Despite her conflict with the Regent King Xiao Heng, who is suffering from a cold poison and holds military power, they accidentally have a relationship in a palace side hall due to the Virtuous King's scheme. The Virtuous King and his daughter, Su Huan, repeatedly frame Su Jin. When Su Huan attempts to cast a fire silkworm curse, Xiao Heng saves Su Jin and discovers her true gender, choosing to protect her instead. As the border crisis escalates and the Virtuous King betrays the nation, Su Jin takes command and, with Xiao Heng's inside support, executes the Virtuous King and defeats the Western Frontier. Upon returning to the capital, Xiao Heng backs Su Jin with the late Emperor's will. Su Jin ascends the throne as the Empress, ruling for 38 years without marriage, while Xiao Heng remains by her side until his death, where they are buried together.