There has been a prophecy throughout the Silla era that the royal blood won't have male descendants once twins are born in the royal family. When the twin daughters, Cheonmyeong and Deokman, are born, King Jinpyeong hides Deokman away from Silla and makes her live in the Taklamakan Desert in China, making it impossible for Mishil to trace her. Deokman starts to wonder about her origin and birth, so she disguises herself as a man and enters Silla. Princess Cheonmyeong believes Deokman is a man, so she has Deokman be a member of Hwarang. At Hwarang, Deokman meets Yusin, who contributes to the unification of the three countries afterward, and cooperates with him to drag Mishil down. Amidst the conflict with Mishil, Deokman's identity as a princess of Silla is revealed. When Deokman escapes to live, she meets Bidam, the son Mishil has abandoned. Deokman joins hands with Yusin and Bidam to topple Mishil. Check out if Deokman succeeds in becoming a clever leader to rebuild Silla.