Two modern best friends transmigrate into a pair of sisters sent by an enemy kingdom for a political marriage, but who are actually spies. They are married off respectively to the cold-faced God of War, Prince Rui, the elder brother, and the charming yet scheming Prince Jing, the second brother. The two princes are deeply wary of these marriages, but they never imagine that the woman the elder brother considers an elite spy is a pure bookworm obsessed only with knowledge and utterly clueless about romance and conspiracies, while the innocent, love-brained girl the younger brother hopes to manipulate is actually a master of human nature who turns the tables on him at every turn. Thus begins a sweet battle of misunderstandings and counterattacks.