Under the oppressive Japanese colonial rule, Deok-hye, the last Princess of the declining Joseon Dynasty, is forced to move to Japan. She spends her days missing home, while struggling to maintain dignity as a princess. After a series of failed tries, Deok-hye makes her final attempt to return home with help of her childhood sweetheart, Jang-han.

On a live music radio show, a letter arrives from the 23 years in the past. Through the letter, the first love and friendships of five friends are revealed.

The movie depicts the three months before Choong-nyung (the future Sejong the Great) becomes king. The Annals of the Joseon Dynasty, which follows the history of the Joseon Dynasty between 1413 and 1865, leaves out records of this crucial period. While future generations would come to know him as King Sejong, the legendary figure who created the Korean alphabet and advanced the country’s scientific research and law, Prince Choong-nyung was originally dismissed as a reclusive bookworm. When his older brothers Yangnyeong and Hyoryeong fail to impress their father King Taejong, the king makes a royal command for Choong-nyung to become the next ruler of the kingdom instead.