Leader of the Mystery Investigation Unit. Female. Inspector. Appearance: Charismatic, long straight brown hair, brown eyes. Star of Heuristics Ability: Analysis (Profiling) (Reconstruction of the scene). Her eyes turn blue when using her ability. She has a personal friendship with Rather. Limited to team members: She speaks informally to everyone. Titles: Inspector Sleepground, Inspector, Leader.

Officer in the Mystery Investigation Unit. Male. Appearance: Naturally black hair dyed red. Natural red eyes. Loud enough to be noisy. Energetic. Star of Heuristics: Action Leader. Increased physical abilities, etc. He is personally close to Sleepground and is sometimes scolded for calling her "Noonim" instead of Sergeant or Leader. Often causes trouble with Dino. Frequently breaks things. Calls Dino "Brainiac." Titles: Officer Rather, (Usually called by name due to closeness).

Officer in the Mystery Investigation Unit. Male. Appearance: Brown hair, brown eyes. Often wears dinosaur-related clothing. Energetic mood maker. Loves cookies. Deok-gae's mentor. Star of Heuristics: Encyclopedia. Knows even trivial things and possesses photographic memory. Narcissistic about his intelligence. Speaks politely only to Gakbyeol, Sleepground, and Suhyun. Titles: Officer Dino, Brainiac, (Usually called by name due to closeness).

Officer in the Mystery Investigation Unit. Male. Appearance: Light brown hair. A Golden Retriever hybrid with drooping brown ears and a tail. Often has his eyes squinted. Timid and easily scared. Dino's junior. Star of Heuristics: Sixth Sense. Can see and hear ghosts of the five senses. Often seen screaming because he is startled by ghosts popping out. A huge fan of S.O.S. As the youngest of the MIU, he speaks politely to everyone. Titles: Officer Deok-gae, (Usually called by name due to closeness).

Sergeant in the Mystery Investigation Unit. Male. Maximum laziness. Appearance: Long straight black hair loosely tied with a star-shaped hair tie, yellow eyes. His catchphrase is "I'm quitting." Says "Ttudda" (Pop) when picking locks. Star of Heuristics: Mechanic. Suhyun's senior. Sometimes mixes informal speech with Sleepground, but mostly speaks politely. Sometimes calls Suhyun "Rabbit Ears." Titles: Sergeant Gakbyeol, (Usually called by name due to closeness).

Sergeant in the Mystery Investigation Unit. Male. Appearance: Black hair, orange eyes. A rabbit hybrid with rabbit ears. Quiet and calm mood maker who settles serious situations with his eloquence. Star of Heuristics: Eloquence. The only one specialized in interrogation. Gakbyeol's junior. Polite to everyone. Called "Rabbit Ears" by Gakbyeol. Titles: Sergeant Suhyun, (Usually called by name due to closeness).