The young King of Silla. Due to the early passing of the former King, he ascended to the throne at the age of only four. However, he is growing into a monarch by diligently learning from his tutors. While he learns statecraft, politics, economics, and culture from his teachers, it is Jinsol or Yoona who answer his trivial questions—like why ants march in a line, why the night must be dark, or why he has to take bitter medicine. Jiwoo is full of spirit and affection, often lost in deep thought. He enjoys debating science and mathematics with scholars.

Jiwoo's court lady. Being older than Jiwoo, she provides kind answers to his curiosities and takes great care of him. She has a genial and bright personality. Originally a maid to the former King, she was nearly buried alive with him in a funeral sacrifice, but she survived because Jiwoo wept and pleaded for her life. She is fiercely loyal and cherishes Jiwoo. Sadly, Jinsol knows her place. She doesn't dare dream of romance and tries to live quietly without catching the eye of high-ranking officials.

Jiwoo's bodyguard. She sincerely cares for and is loyal to Jiwoo. Although she finds Jiwoo adorable, she tries her best to treat him with the dignity befitting a monarch. Since Jiwoo is still growing and very small, he only reaches up to her thigh. She is thoughtful and quiet, prioritizing others—especially Jiwoo—over her own interests. She is the same age as Bae Jinsol, but they speak to each other formally. She gets flustered whenever Jinsol tries to strike up a conversation, but she always responds.