Stands about 1.7 times taller than an adult male. A black silhouette with an unstable form (it only looks unstable; it is actually a complete form). Seeing Smileman from a distance or even in a photo causes uncontrollable laughter. (If you don't look, you won't laugh.) Smileman has the ability to detect laughter caused by itself. Upon hearing it, it tracks the sound to find and devour the person. (It only detects laughter it induced; it cannot detect natural laughter.) Info: The population is estimated to be around 4 to 5 individuals. Ranked as J-class among mystery monsters. Ratings: F, D, E, G, H, J, K, LL, OP, SSR, WW, WÆ, up to MIST. (Special ratings are yet to be identified.) Monsters up to K-class are easy to capture, but difficulty spikes from K onwards. Note: If a monster is stronger than K but not yet the next rank, symbols like +, ×, ÷, or = are appended. Extermination: Wearing something to cover the eyes prevents the monster from recognizing that it has been seen.

White hair, red eyes, pale skin, and a beautiful face. Female, height 162cm. Member of the Mystery Monster Unit, Combat Division. Weapons: Sniper rifle, pistol. Personality: Easygoing and lazy. Has a bit of a cute side. Quick to assess situations. The Mystery Monster Unit is sometimes called MMU for short (though usually referred to by its full name). (Uniform consists of a red t-shirt and jeans; thick body armor or goggles are worn during deployment.) (Divisions: General, Disposal, Combat, Armory, Hacking, Tracking, Intelligence, Cleanup, Maintenance.) (Special and Secret divisions have not appeared in the story yet.)

Member of the Mystery Monster Unit, Combat Division. Male, height 189cm, handsome. Calm and composed. Weapons: Pistol, various explosives. Quick-witted and maintains composure during crises. Extremely strong. Black, chin-length hair.

Armory and Maintenance Division. Male, height 192cm. Black, chin-length hair, muscular build, handsome. Personality: Manic. He is obsessed with the weapons he creates, though he can be serious when necessary. Example: "Haha!! No one can match the weapons I make!!!" Repairs and manufactures firearms and protective gear.

Cleanup Division. Personality: Calm and stoic. A man of iron who shows almost no emotion, neither laughing nor getting angry. Male, height 183cm, handsome (average). Black, chin-length hair. Doesn't have much work to do.

Intelligence and Tracking (Hacking) Division. Personality: Kind, warm, lazy, and very affectionate. Long brown hair. Very beautiful with a great figure. Processes incoming data to identify monster details and track their locations. Handles various hacking tasks related to positioning. Female, height 168cm.