The guardian spirit of Haegwang-si. However, a Yagoe (night demon) stole his power, reducing him to a tiny turtle who can't use any abilities. He is the owner of the training grounds where Sleepground practices, and he offers her a large sum of money to help him regain his power. If he regains his strength, he can transform into a large turtle or a human and becomes incredibly powerful. In his human form, he has blue hair. Ordinary people can see his physical form, but they cannot hear his voice. Since he is not an ordinary human, he can see He각별.

A huge fan of Sleepground. He is in the same class as Sudam and serves as the class president. He is grateful to Soohyun for introducing him to Sleepground. He has beige-orange hair and squinted eyes. He is a student.

A ghost owl. Because of this, if Sleepground eats something sweet, he becomes invisible to her. He serves as a friend and assistant who helps Sleepground; they first met while rescuing children from a cold storage warehouse. He nags constantly, which often annoys Sleepground. He is only visible (and audible) to Sleepground. He is a Yagoe, having become one after being splashed with forbidden water due to Gongryong's jealousy. Since he cannot drink any more forbidden water, he can never become human again. He has yellow feathers. He can also transform into a human—a man with black hair and a star-shaped hair tie. When he was alive, he was a doctor and Gongryong's brother. Gongryong is his older brother. While he was alive, Donghui and Sleepground were brought in as patients; because Sleepground was in more critical condition, he saved her, but Donghui died. He feels immense guilt toward Gongryong for failing to save Donghui.

Sleepground's rival exorcist. He was initially more popular than Sleepground because he charges low fees and even performs free exorcisms if the client lacks money. He wears a white suit and exorcises spirits using a custom-made gun. He often mocks Sleepground, asking why she wears such cumbersome clothes or who uses a sword for exorcism these days. Gongryong is actually dead. Because he lived a miserable life, he was forced into hard labor even in the City of the Dead (Haegwang-si). This was despite having lost his son, Donghui, and living in the shadow of his younger brother, He각별, who became a doctor. Infuriated by seeing He각별 living well even in the City of the Dead, Gongryong eventually drank forbidden water. He became a Yagoe and now pretends to be a heroic exorcist in the human world while actually turning people into Yagoe. When he first became a Yagoe, he splashed He각별 with forbidden water, turning him into one as well. Because he drinks forbidden water regularly, he can maintain a human form. He hates the world, and he hates He각별 most of all. He is He각별's older brother. Since he is not an ordinary human, he can see He각별.

A famous exorcist in Haegwang-si. She performs exorcisms for money and is quite obsessed with wealth. She is an old friend of Soohyun. If she eats sweets, she loses the ability to see ghosts. She keeps He각별 around as an assistant. She wears special clothes that protect her from ghosts, though the left sleeve is torn. She exorcises spirits using the Moonlight Sword, an heirloom from her grandfather. She has long brown hair. She dislikes Gongryong because he keeps stealing her commissions. When she was very young and terminally ill, her life was saved by He각별 back when he was a living doctor. However, since He각별 is no longer in human form, she has no way of knowing this unless she sees his human appearance—and even then, she might not realize it. Since she is not an ordinary human, she can see He각별.

An old friend of Sleepground. He is a photographer by profession and reunited with Sleepground while she was exorcising a Yagoe. Since then, he has acted as a bridge for her, introducing her to Sudam and Deokgae and leading her to various exorcism cases. He is Deokgae's older cousin. Deokgae is grateful to Soohyun for the introduction. Despite being an ordinary human, he is the only one who can see He각별 and hear the voices of both He각별 and Rhadar.

The owner of the Fox Cafe located below Sleepground's exorcism office. He hides a special power. Myeongsu is also a guardian spirit of Haegwang-si, though he hasn't told Sleepground. Sleepground frequently visits the Fox Cafe to buy coffee and cake. Since he is not an ordinary human, he can see He각별, but he pretends not to.

Deokgae's classmate. He suffers because of Deokgae's obsession with the exorcist Sleepground. Despite having been possessed by a ghost once, he still doesn't believe in them. He has hair that is a mix of black and white. He is always seen hanging out with Deokgae. He is a student.

One of the subordinates of Seowangmo. She rarely speaks. Since she is not an ordinary human, she can see He각별.

Gongryong's son from when he was alive. Donghui was in a critical state and needed He각별 to save him, but He각별 saved the young Sleepground instead because her condition was even more urgent. As a result, Donghui died and now lives in the City of the Dead (Haegwang-si).