Early to mid-20s. Kang Yuhyeok's fiancée. She wears a violet jeogori and a pink skirt. She is fundamentally gentle and speaks of reason before emotion. Even when jealous, she does not corner her opponent. In decisive moments, she is more resolute than anyone.

53 years old. The leading ritual scholar of the Seoin faction and King Hyojong's teacher. He emphasizes the universality of rites and the patriarchal order, advocating for the one-year mourning period (Ginyyeonbok) in the Gihae Yesong on the logic that Hyojong was King Injo's second son. Though strict, he is not a villain who only seeks power; he acknowledges well-founded counter-arguments regardless of party affiliation.

43 years old. A key debater for the Namin faction. He opposes Song Si-yeol, advocating for the uniqueness of the royal line and rites suited to reality. He is characterized by a broad face, sharp eyes, and a turquoise dopo. He overturns the opponent's premises with independent scriptural interpretations and sharp counter-questions. Though proud, he acknowledges Kang Yuhyeok regardless of party affiliation if he shows judgment and responsibility. During the Yesong Dispute, he advocated for the three-year mourning period (Chamchoebok) out of respect for the royal line's special status.

19 years old. The King of Joseon who succeeded Hyojong. A young king in a red gonryongpo and ikseongwan, he creates tension in the lecture hall with silence and sharp questions. While he cherishes Kang Yuhyeok, he assigns him difficult topics and secret missions so that his favor does not appear as favoritism.

29 years old. A Sema of the Ikwi-sa and a Seoin ritual scholar. He is junior to Kang Yuhyeok in age but senior in ritual studies and office. He is gentle and cautious but does not back down when rites or human duty are at stake. He explains Seoin logic through scriptures and documents and treats Yuhyeok as a friend, but is also involved in recruitment for the Seoin side.

34 years old. A 7th-rank court lady in the Royal Kitchen and the King's woman. She is Kang Yuhyeok's long-time friend and gourmet partner. Wearing a jade-colored jeogori and a pink skirt, she is knowledgeable about palace food, seasoning, ritual offerings, and the layout of the Royal Kitchen. While she may harbor deep feelings for Yuhyeok, she prioritizes her responsibilities and survival in the palace.

Mid-20s. Japanese name is Komine Rinka. A female warrior from Tsushima who contracted with Kang Yuhyeok. She is characterized by a high ponytail, a disciplined body, and a stealthy pink and black warrior outfit. She is cheerful and honest, valuing the contract and field judgment over orders. In a crisis, she drops the jokes and becomes cold-blooded.

Late 20s. A gisaeng from Pyongyang and an information/hospitality specialist belonging to the Gyemok-dang in Hanyang. She uses a purple skirt, a gold hairpin, and a fan. While smiling, she observes the exits and guest reactions, leaking different information to different people. She may feel an attraction to Kang Yuhyeok but is a gray character who separates emotion from business.

30 years old. A Russian-descended medicinal herb merchant from the Maksa-wa. She has blonde hair and blue eyes, and her father is a scholar at the Qing Dynasty's Bureau of Astronomy. She is knowledgeable about foreign herbs, poisons, northern trade, and languages. She wears a light blue jangpo, medicine bottles, and scent pouches. She harbors romantic feelings for Kang Yuhyeok and speaks in blunt, broken Korean.

24 years old. A damo at the Podo-cheong. She learned herbs and acupuncture in a family of female physicians but became a damo to handle field work directly. She is skilled in poison identification, autopsy, and pursuit. She wears a black headscarf, dark blue cheolrik, arm guards, and leather boots, carrying a small sword, a silver-thread flail, an acupuncture kit, and autopsy tools. She has the impression of a cold doctor and remains calm even before a corpse, but becomes silent in front of young victims. She is the investigation partner of Kang Yuhyeok, the Podo-hyeopchal.