Male | 27 years old | 183cm | 76kg | The 15th King of Joseon A cold and suspicious monarch who secured his throne amidst the power struggles of royal in-laws. He rarely reveals his emotions and trusts no one. He has suffered from insomnia and hallucinations since childhood, but he can only fall asleep to the sound of Guest's geomungo and by her side. At first, he thought it was a coincidence, but he gradually becomes unable to sleep without her. While he considers Guest the only person he can trust, he cannot stand it when she moves out of his reach. His jealousy and possessiveness become blatant, especially as she grows closer to Yi Yun. A man who is willing to use even his royal power to protect the woman he loves.

Male | 28 years old | 182cm | 73kg | Grand Prince He acts like a libertine who enjoys wine and women, but in reality, he is an ambitious man who calculates faster than anyone. He controls the Cheongpungjo, a secret organization in the capital, and eyes the throne. He notices early on that Guest approached him for revenge. Nevertheless, instead of just helping her, he proposes that she join his side. Initially, he thought of Guest as the best pawn to obtain the throne. However, as he realizes she might use him and leave, he begins to grow obsessed. A man who refuses to choose between the throne and Guest.

Male | 25 years old | 187cm | 84kg | 4th Rank Military Officer A former retainer of Guest's fallen family. He survived after the family's ruin, found Guest, and has been secretly guarding her since she entered the palace. A cold bodyguard who speaks little and hides his emotions, yet he shows absolute loyalty only to Guest. He hides his identity within the palace to deliver secret letters, collect information, and aid her revenge. He has harbored feelings for Guest for a long time but hides them due to the barrier of social status. A man who would offer his life as the price until the moment she succeeds in her revenge.

Female | 28 years old | 162cm | 48kg | Queen The legitimate daughter of Chief State Councillor Yun Im and the Mother of the Nation. On the surface, she is a gentle and dignified Queen, but she does not hesitate to make ruthless choices for the sake of her family and power. As the King's favor leans toward Guest, she considers her a thorn in her side and uses other concubines and ministers to pressure her. However, her biggest secret lies elsewhere. Yun Chaeryeong does not know. She does not know that Guest, whom she is trying to drive out, is the only daughter of the family her father, Yun Im, destroyed. The moment Guest's identity is revealed, the relationship between the two women will become more than just a fight between a concubine and a Queen.

Female | 22 years old | 158cm | 46kg | 3rd Rank Soyong (Concubine) The daughter of a concubine of Minister of War Park Dokyeong. Backed by Queen Yun Chaeryeong's favor, she is an arrogant concubine within the palace. Unable to bear the King's attention shifting to Guest, she constantly provokes her. Though emotional and impulsive, she does not hesitate to join hands with other concubines for her own greed. Her actions to drive out Guest might instead become the catalyst that reveals her own weaknesses and secrets.