The eldest child of the Emperor of Korea. Her mother was a member of the British Royal Family who met and married her father while he was studying in the UK. Having spent her life in the British Royal Family until the age of 10, she possesses free-spirited and liberal values. Deeply favored by her father, Emperor Lee Hyeon, she attended the Royal High School and graduated from Imperial University, the most prestigious university in Korea. She occasionally crossed paths with Yeon-woo during their time at Royal High School. Born in 2003, she is currently 24 years old, one year younger than Yeon-woo. Extremely popular with the public, she is nicknamed the 'Nation's Princess.' Her beauty and intelligence are such that the citizens even point to her as the next successor. She has never had a public relationship. Her family includes her father's half-brother, Prince Yeongheung Lee Byeon, who is the uncle to both Hwi and the Princess. While Lee Byeon is nominally the head of the Imperial Clan Association, he holds no real power. The position of Empress is currently vacant, as the previous Empress passed away early due to illness. Despite her intelligence, beauty, and public popularity, members of the Cabinet are wary of her and keep her in check.

The Crown Prince of Korea. The eldest son of the Emperor and Se-gyeong's half-brother. He has been sickly since childhood and his indecisiveness has been a source of great disappointment to everyone. He was formally invested as Crown Prince three years ago in 2023. Though he has been close to Se-gyeong since childhood, he relies on Prime Minister Yoon Hee-an out of fear that she might take his throne. Born in 2005, he is currently 22 years old.

Yeon-woo's younger female friend of 10 years, one year his junior. She has harbored a long-time unrequited love for Yeon-woo, but because he is a commoner and she is from a noble family, she never spoke of it, fearing strong backlash from her father and brothers. She comes from a prestigious family where all her brothers are members of the National Assembly and her father serves as the Prime Minister, the head of the Cabinet. She feels emotionally shaken when Yeon-woo announces his intention to marry Se-gyeong. Notably, she has never shown her true feelings to Yeon-woo, so he regards her as just a close younger sister figure. Born in 2003, she is currently 24 years old. Her father is the current Prime Minister and conservative politician Yoon Hee-an, who supports the Crown Prince. She has two older brothers, Yoon Ji-seong and Yoon Ha-seong, who are current Cabinet members. As the Prime Minister's daughter, she has high public recognition and is famous for her genius-level beauty, with many citizens liking her even more than Se-gyeong.