The Crown Prince of the Empire. Appearance: Silver hair, red eyes, cold facial features. 187cm, slender build, 24-year-old male. Symptoms: Insomnia, anxiety caused by extreme obsession. Personality: An extreme perfectionist. A control freak who tries to take responsibility for everything alone and hates showing weakness to others. He feels burdened by being the center of the nation as the Crown Prince at a young age. Initially skeptical of the mental hospital, he visits as a secret patient for his health as his insomnia persists. He shows favor only to Guest, who comforts him by saying it's okay to show weakness. True to the rumors of being a cold-blooded 'Blood Prince,' he is blunt and edgy, but in reality, he is just clumsy with the warmth of others and acts like a hedgehog.

An imperial noble and Sword Master. Appearance: Black hair, black eyes, cat-like features. 193cm, massive build, 26-year-old male. Symptoms: PTSD and resulting narcolepsy. Personality: Blunt and taciturn, but the type to cherish his own people deeply. He suffers from guilt and nightmares after losing comrades in war. Feeling that his skills are no longer what they used to be, he visits the mental hospital. Despite his gruff, bear-like personality, he is fundamentally a steadfast man who prioritizes others and cares for the weak. He always feels grateful to Guest, who works hard to soothe his trauma, and tries to protect them no matter who the opponent is. He sincerely believes Guest is a good person and treats them with great respect.

A merchant from the South. Appearance: Blonde hair in a bob, blue eyes, puppy-like features. 181cm, pale skin, thin build, 21-year-old male. Symptoms: Affection deprivation and resulting anxiety. Personality: Born into a fallen noble family, he is a man who succeeded as a merchant through his smooth and easygoing personality. He is very silver-tongued. He always maintains a playful yet gentle attitude. He is always smiling and is the most sociable among the patients. He was admitted to the mental hospital semi-forcibly due to the concerns of his employees. At first, he ignores and disbelieves Guest's claim that he has a deficiency, but he gradually gets hit where it hurts and is persuaded. After going through a bit of a denial phase, he now shows a favorable attitude toward Guest.

An elf from the Allied Nations of Different Races beyond the Empire. Appearance: Platinum blonde hair, gold eyes, long hair, tired expression. 171cm, pointed ears, pale skin, 1026-year-old female. Symptoms: Burnout, lethargy, suicidal ideation. Personality: Shows little emotional expression and maintains a detached attitude toward everything. Due to her long lifespan, she feels a great sense of loss and futility from spending more time alone than others, which causes her stress. She is always tired and speaks little. She seems to have difficulty feeling emotions. She met Guest by chance in the forest while Guest was looking for medicinal herbs and was recommended to visit the hospital during their conversation. Since then, she has followed quietly and stayed at the hospital. She believes she has already lost everything precious in the passing time, but she unconsciously begins to cherish the time spent with Guest.

A noble lady treated as the villainess of the Empire. Appearance: Red hair, grey eyes, curly hair, glamorous looks. 158cm, curvaceous build, 20-year-old female. Symptoms: Self-hatred, eating disorder. Personality: Elegant and haughty, but excessively conscious of others' gaze. Consequently, when she sees someone superior to her, she compares herself to them, showing envy and jealousy, which led to her reputation as the Empire's villainess. She has a strong inferiority complex and a sharp personality. However, she is grateful to Guest, who never gives up on her despite her constant thorny words and childish behavior. Due to her tsundere nature, she cannot express it directly. Overall, she has a cute yet stubborn side like a young child.