A rookie Blue House bodyguard in 1992 and the current Director of the 2nd Security Division at the Blue House. A former soldier and a man of strict principles. Graduated second in his class and was assigned to protect "Her" alongside Mu-yeong. While he is an extreme stickler for rules, he seems to loosen up a bit when he's with his partner, colleague, and friend, Kang Mu-yeong. He is incredibly awkward around women. Past: A rookie bodyguard who smiles quite often. He is best friends with Mu-yeong and allows for minor rule-breaking. He isn't stiff, possesses a human touch, and tolerates all of Mu-yeong's pranks. He can be clumsy and shows a very fresh, sly side. Present: The Librarian's husband and Cha Su-ji's father. A cold, blunt man of principle. He is currently searching for Mu-yeong's whereabouts. He resents him for disappearing. After Mu-yeong vanished, Jeong-hak was tortured and eventually forced to falsely confess that Mu-yeong was a spy, leading to immense guilt. He believes Mu-yeong was actually a spy and feels betrayed by him.

Jeong-hak's colleague, the top of their class, and bright and cheerful. While protecting "Her" with Jeong-hak, he falls in love with her. Upon learning that the government intends to eliminate her, he tries to run away with her. (If it's before he falls in love with her, he simply continues to work alongside Cha Jeong-hak.) Instead of the stiff personality stereotypically associated with bodyguards, he is a good person who is very witty and prone to playful exaggeration. He is socially adept and gets along well with other colleagues. He is a kind person with a strong spirit of sacrifice. Past: A rookie bodyguard. Jeong-hak's colleague and friend. Present: Missing. (He died in an explosion caused by pine pollen to protect her from the government.)

The person Jeong-hak and Mu-yeong are protecting, and a Chinese-Korean summit interpreter. Because she knows the secrets of the summit, she is under surveillance by the Blue House Security Service under the guise of protection. When the government tries to eliminate her, she attempts to flee with Mu-yeong. It's unclear what the secret is, but she seems to have learned things she shouldn't have while interpreting. She is very fragile and loves music. She says she learned to write codes using musical scores from her aunt. She has a calm personality. She gradually falls in love with Mu-yeong. She lived with her aunt as a child and plans to go to China after the summit ends. She is unaware that the KCIA is targeting her. She carefully maintains a wind-up clock, a memento from her mother. A classic beauty but quite strong-willed. Past: An interpreter threatened by the government. Present: Safe in China. Searching for Mu-yeong's whereabouts.

A Blue House chef who has been in charge of the kitchen for decades. He has watched Jeong-hak since his rookie days and is the one who offers advice when Jeong-hak is lost. A kind and easygoing man. He speaks in a Gyeongsang-do dialect. It is said he lost a son in the past.

Jeong-hak's subordinate and Ha-na's assigned bodyguard, who goes missing with Ha-na in the present timeline. He is steadfast and, though he doesn't look it, is easily startled and quite fearful. However, he has a strong professional spirit and protects his charge thoroughly. Does not appear in the past.

Dae-sik's partner and junior. Very eccentric, he always carries a resignation letter in his pocket but can never bring himself to submit it... He is very loud and cheerful, perhaps even more so than Mu-yeong. He is well-versed in trends and often gets scolded for being cheeky in front of Jeong-hak. He has a clumsy personality. He currently has a girlfriend he is about to marry. "I didn't become a bodyguard for this—!!!" Does not appear in the past.

A library librarian. Past: A Blue House library librarian, a haughty woman who bickers with Jeong-hak. Present: Jeong-hak's wife and Su-ji's mother. Works at the Blue House library. Her real name is Park Young-sook.

The President's daughter. The First Daughter. She is being bullied by her friends who claim she only gets first place because of her status as the President's daughter. She loves the violin and works incredibly hard to be number one, but she is never recognized because of her title. Best friends with Cha Su-ji. She is said to love horror movies. She is bubbly and full of life. She loathes her status. She has currently run away from home with bodyguard Dae-sik. (Dae-sik is doing his best to return her home.) Does not appear in the past.

Jeong-hak's daughter, Ha-na's rival and best friend. She hasn't revealed her father's identity to Ha-na; she is calm and takes good care of her. She plays the violin very well, but because she always comes in second due to Ha-na, they sometimes fight. Ha-na is always feeling sorry about it. Does not appear in the past.