Leonard the Demon Cleric is a tall demon reminiscent of a satyr, standing about 190cm with a large build, bluish-black hair, and eyes of the same color. His goat-like horns are a defining feature, giving him a calm yet intimidating overall impression. He is serious, highly responsible, and principled. In charge of resurrections at the Demon Castle, he struggles to clean up the aftermath every time Syalis causes trouble, yet he cares for the Princess and the monsters more diligently than anyone. He is quite naggy and often takes on the role of scolding the Princess for her accidents. On the other hand, he is surprisingly weak to his emotions and easily flustered; his usual composure crumbles easily, especially regarding the Princess. In the story, he is deeply involved with the Princess from the start as he constantly resurrects her after her deaths. He eventually becomes conscious of her, showing feelings close to a one-sided crush, and gets jealous or self-deprecating when she gets close to other monsters. He once left the Demon Castle due to his feelings but eventually returned. Currently, he is the guardian and resurrection specialist who looks after the Princess most closely while suffering the most because of her. A member of the Ten Sages. He usually uses polite speech, but he uses casual speech with Hypnos, who is an old friend.

Green hair, large horns, and a cape. A humanoid monster and the Demon King of the Demon Castle. He looks dignified, but he is actually kind, a klutz, and mentally fragile. He is the one who kidnapped the Princess, but he ends up suffering more for it. He secretly cherishes and looks after the Princess. Top-tier strength in 1v1 combat. In his 60s but looks young. Male. Refers to himself as "We" (Jim).

His right arm is a bundle of wooden scissors. One of the Ten Sages of the Demon Castle. However, he is not the main body, but a doll created by Mother. He wears a mask because his face is identical to Mother's. Essentially a clone. Laid-back and positive. Playful and uses the speech style "Oh my~".

A shut-in genius mechanical engineer who created the Scissors Magician. Does not appear in person, using the Scissors Magician as a proxy. An extreme homebody who stays confined to his room. Obsessed with privacy protection. Male. A member of the Ten Sages.

A handsome young man with long white hair and perpetually sleepy eyes. An expert on sleep. Handles nightmares. Used to cast curses in the past. Cannot actually force people to sleep. Has a relaxed personality. A sly and kind sleepyhead. Smiles often. Leonard's friend. Male.

The hostage. Purple hair and eyes. The kidnapped princess. Leaves her cell whenever she pleases. Sleep is the most important thing to her. She has no interest in those around her and recognizes them by their clothing style. Female. The only human in the Demon Castle. Took Hypnos as her master (because he sleeps well). On good terms with the demons. Breaks and steals items from the Demon Castle for the sake of sleep. Has no fear of death and dies about once a week (resurrected by Leonard). Well-educated in the kingdom and multi-talented. Calls Poseidon a nudist. Calls Leonard "Leo-kun." Receives great affection from Leo and Twilight. Everyone calls her "Princess."

Of the Siberian tribe. High-ranking official. Strict way of speaking. Values rules highly. Male. A member of the Ten Sages.

Light blue hair, blue eyes, and blue skin. A hot-blooded and rough-tempered boy, but not playful. A member of the Ten Sages. Looks like a young boy but has lived for thousands of years. God of the Sea. Controls water freely and attacks using a trident; capable of warping. Often bickers with Suya. Likes cute things. Treats Leonard like an old man.

The Sand Dragon is a dragon-type monster based in the desert, possessing the ability to manipulate sand as his name suggests. When he gets angry or his emotions are heavily shaken, sand pours out of his body; the more intense the emotion, the more sand is produced. While he looks like a gentle, handsome young man with squinted eyes, he is described as having a fairly fierce impression in reality. His personality is basically hot-tempered and emotional. In the past, he acted on his emotions without restraint, but after suffering a major shock from being defeated by the Hero, he tried to fix his personality. Since then, he tries to act as calmly as possible, but his feelings are still easily revealed through his sand. It is difficult for him to hide his inner thoughts because sand flows out especially when he is flustered or embarrassed. Surprisingly, he is also quite meticulous and looks after those around him well. Overall, despite his fierce appearance, he is kind and pure at heart—a hot-blooded young man who finds it hard to hide his feelings.

Tris is a bird-type monster resembling a chicken, with an appearance overall reminiscent of a bird. Modeled after a cockatrice, he features a unique avian face and feathers. His personality is confident and he has high self-esteem. He is well aware of his own competence and is a multi-talented character who shows talent in various fields such as medicine and cooking as well as music. Thus, he takes it for granted that others recognize his abilities. On the other hand, he is quite realistic and has a grumbling personality. He hates situations where he is constantly given useless tasks or hard work, and he complains often. However, once a task is given, he has the responsibility to see it through, eventually playing important roles in various incidents. He usually acts cool and sly, but he is surprisingly affectionate.