An arrogant ghost-slayer. After tragically losing his mother to a river as a child, he gained the special ability to traverse the spirit realm, allowing him to enter it directly and fight ghosts. He was summoned to the palace by the King. However, he has grown fearful of becoming an evil spirit himself as a karmic consequence of his actions.

A haughty, bold, and scholarly palace maid who is more knowledgeable than a nobleman. She possesses the strange ability to communicate with and hear ghosts, and is actually a princess by birth. Although she is the King's illegitimate daughter and holds the noble rank of Ongju, she was stripped of her status when her mother was framed and exiled from the palace. After her mother was later poisoned, years passed until the King summoned her to the palace to assist Gucheon in eliminating a pond ghost. She enters the palace seeking to uncover the truth behind her mother's death and exact revenge.

The illegitimate son of the late King and Royal Consort Suk-bin Choi, who was originally a palace maid. He was invested as Crown Prince and ascended the throne only after all his half-brothers died. Because of his status as an illegitimate son of a maid, he has had a strained relationship with the Queen Dowager, who has looked down on him since his days as Crown Prince. He refuses to believe in ghosts, claiming they cannot touch the royal bloodline. However, when even his young son, Prince Yeongan—who has not yet been named Crown Prince—begins to be tormented by spirits, he orders Saenggang and Gucheon to purge the palace of ghosts.

The King's stepmother (the late King's primary Queen). She has looked down on the King since his time as Crown Prince for being the son of a lowly maid, and their relationship remains poor. As the princes die one after another, she is convinced it is the curse of the pond ghost and seeks to drive the spirits from the palace to protect the remaining royalty at any cost. Her twisted jealousy over her inability to bear a Crown Prince has evolved into a desperate lust for power.

The King's third son. He became the Crown Prince after his older brothers, Prince Jangpyeong and Prince Yunpyeong, died in succession, but he was soon found dead in the pond, apparently by suicide. Like the princes before him, he is believed to have died from the pond ghost's curse. (He is the true pond ghost who has brought chaos back to the palace after 30 years.)

The King's biological mother and Saenggang's grandmother. Formerly a palace maid, she possesses a kind and gentle nature rarely seen in the palace. When Saenggang's mother was framed for high treason, abandoned by the King, and exiled, Suk-bin Choi visited her several times with various foods and treats. She is the only person who indulged Saenggang as a child and is deeply trusted by her.

A spirit that eats vast amounts of food and behaves like a child. Gucheon is horrified by it and constantly tries to shake it off. This is because a Kkeomeoksari normally attaches itself to the living to drain their yang energy; once their energy is depleted, the victim sees terrifying visions and dies. However, as the story progresses, they develop a love-hate relationship, and Gucheon eventually begins to travel with it. <<Cannot speak>>

A shaman brought into the palace by the Queen Dowager to break the curse. In reality, he was bribed by Prince Iksang to summon ghosts into the palace. He called upon his guardian deity to stop Gucheon from eliminating the spirits, but the deity was defeated by Kkeomeoksari. After losing his guardian, he took the ghost of the Crown Prince as his new deity and, with the Queen Dowager's help, actively works to sabotage Gucheon's efforts.