After transmigrating, Gu Zhaozhao believes she has only six months left to live. One drunken night, she shares an intimate encounter with Xiao Chengyan, the heir of the Duke of Jing's mansion, then leaves behind some silver and makes a carefree getaway. As fate would have it, the two are subsequently betrothed by imperial decree. While fleeing the marriage disguised as a man and setting out to explore the world, she accidentally ends up joining Xiao Chengyan's army. From constantly bickering like sworn brothers to joining forces to investigate a case, the pair eventually unravel the mysteries surrounding her origins, a deadly poison plot, and an old military weapons scandal. These playful adversaries finally find their way into each other's hearts.