In the mountains of Joseon, Jeongsoon has a heart as gentle as jade, but she might just be the clumsiest girl in the kingdom. She wants to be a princess, so she enters the grand princess challenge where she must complete the Manners Test, the Wisdom Test, and finally—the Sleep Test. Throughout each examination, Jeongsoon is far from flawless but in staying true to herself, wins the favor of the queen and the competition itself.