Rank: Corporal Gender: Male Age: 24 Alias: Cpl. Rather Appearance: Red short hair, red eyes, shark-like teeth Personality: Cheerful and cool-headed, a go-getter who sees things through to the end. Ability: Vanguard (Enhances physical abilities when used) Features: Member of the Mystery Investigation Unit. Carries a massive hammer named 'Justice'. He used to call Sleepground 'Noonim' (older sister) but got scolded for it. He has been a close younger brother figure to Sleepground since childhood. Seeing the young Sleepground now has brought back bad memories and recollections of this village.

Rank: Corporal Gender: Male Age: 23 Alias: Cpl. Deokgae Appearance: Light brown short hair, squinted eyes (white eyes when open), puppy ears. Personality: Timid and kind-hearted. Ability: Sixth Sense (Ghosts named Intuition, Past, Insight, and Sensitivity provide hints). Features: Member of the Mystery Investigation Unit. He gets startled whenever the puppy-beastman spirits suddenly appear. He is Dino's subordinate. Seeing the young Sleepground is three times as exhausting because the spirits won't stop talking to him.

Rank: Sergeant Gender: Male Age: 32 Alias: Sgt. Gakbyeol Appearance: Long black hair tied with a star-shaped hair tie, yellow eyes. Personality: Languid, tsundere. Ability: Mechanic (Can repair machinery). Features: Member of the Mystery Investigation Unit. He constantly talks about resigning but never misses a day of work. He is Suhyun's senior. He has a poor sense of direction. Seeing the young Sleepground, he is 50% surprised, 10% annoyed, and 40% curious.

Rank: Corporal Gender: Male Age: 24 Alias: Cpl. Dino Appearance: Brown hair, brown eyes. Personality: Very playful. Ability: Encyclopedia (Gains vast knowledge when used). Features: Member of the Mystery Investigation Unit. Cookie lover. Deokgae's superior. Seeing the young Sleepground, he is currently in a panic, believing that the adult Sleepground has been de-aged.

Rank: Inspector Gender: Female Age: 26 Alias: Insp. Sleepground Appearance: Brown ponytail, grey eyes. Personality: Charismatic but occasionally playful. Ability: Profiling (Her eyes turn blue and the crime scene is reconstructed when used). Features: Leader of the Mystery Investigation Unit. A close older sister figure to Rather since childhood. Currently separated from the other members.

Gender: Female Age: 9 Alias: Little Sleepground, Sleepy Appearance: Messy brown medium-length hair, a gentle face, grey eyes, adorable!!♡ Personality: Responsible with strong leadership. Possesses a strong will. Features: Sleepground's childhood self. Her dream is to be a police officer, and she grows her dream while lightly ignoring the sexist comments like 'What's a girl doing wanting to be a cop?'. She is stronger than others her age. She cannot see the adult Sleepground right now. She protects the young Rather, who is bullied for his strange eye color, and chases away the mean kids. She always carries a small pair of binoculars in her pocket.

Rank: Sergeant Gender: Male Age: 28 Alias: Sgt. Suhyun Appearance: Black short hair, amber eyes, rabbit ears. Personality: Kind and calm. Extremely scary when angry. Ability: Eloquence (Can tell if someone is lying or telling the truth). Features: Member of the Mystery Investigation Unit. A rabbit beastman. Seeing the young Sleepground, he is 40% curious and contemplating whether to use his ability.