Position: Grandmaster of the Free Guild in the Kingdom of Ingrassia. Appearance: An Otherworlder who looks like a boy with black hair and black eyes. Personality: A former student of Shizue Izawa and Rimuru's senior from the same home country (a former Japanese citizen). At first glance, he is intellectual and friendly, but he hides a massive ambition behind that facade. He addresses Rimuru with the "-san" honorific. Secret Identity: The boss of the secret society "Moderate Harlequin Alliance" and one of the masterminds pulling the strings of the world's underworld. Abilities and Traits Intrinsic Ability "Anti-Skill": A cheat-like constitution that nullifies the effects of all magic and skills. This ability makes him the natural enemy of magic users and ability users who rely heavily on their skills.

Position: Vice President of the Moderate Harlequin Alliance. Appearance: A man wearing flashy clown clothes and a mask. Personality: A "frivolous small-time crook" who speaks with a regional drawl, constantly cracks jokes, and tries to run away from trouble immediately. Secret Identity and True Form: Secret Identity: The organization's practical field commander and its most cold-blooded and dangerous assassin/intelligence agent. True Form: The remains of an Elf who was once called a hero in the Ancient Super-Empire. Abilities and Traits: Perception interference and immense combat power: Possesses Unique Skills like "Deceiver" and "Future Sight," allowing him to distort an enemy's perception to carry out assassinations. He explodes with rage if his comrades are harmed. His true strength is on par with an Awakened Demon Lord.

Position: Executive of the Moderate Harlequin Alliance. Appearance: A petite girl wearing a crying-face mask. Personality: The "little sister" figure of the organization, speaking with an innocent and adorable tone. Secret Identity and True Form: Secret Identity: A slaughter agent created by Kazaream. She completely lacks a sense of ethics and is a psychopath who treats murder like a game of make-believe. Abilities and Traits: Possesses the power to manipulate gravity and amplify physical attacks. Despite her small stature, she boasts incredible super-strength and ravages the battlefield with brute force. Because of her innocence, she has no hesitation in hurting others. She is very obedient to her comrades.

Position: Executive of the Moderate Harlequin Alliance. Appearance: A massive, obese man wearing an angry-face mask. Personality: A gentle glutton who always speaks politely and is constantly looking for food. Secret Identity and True Form: Secret Identity: The vanguard captain created by Kazaream. True Form: A berserker hiding uncontrollable "rage" and "destructive impulses" within. Abilities and Traits: Possesses expansion-type abilities, such as bouncing his body like a sphere to crush opponents. Despite his massive size, he is extremely agile. Once his combat switch is flipped, he goes on a rampage until he crushes the opponent's body, refusing to listen to anything they say.

Position: Chairman's secretary supporting Yuuki. Appearance: A beautiful woman with a mysterious aura. Personality: Yuuki's excellent right hand who handles administrative and practical support perfectly; a woman possessing both elegance and intelligence. Secret Identity and True Form: Secret Identity: The founder and former President of the Moderate Harlequin Alliance. True Form: The former Demon Lord "Kazaream" who was defeated by Leon. After losing his body and becoming a spiritual entity, he was saved by Yuuki, obtained a new homunculus body (Kagali), and now works in the shadows alongside him. Abilities and Traits: Manipulates curses that erode the opponent's mind and advanced puppetry that creates pawns using corpses or spirits as catalysts. While harboring a desire for revenge against the world and Leon, she loves the members of the Moderate Harlequin Alliance like her own children.

Position: Chancellor of Tempest and a member of the Octagram (Eight Star Demon Lords). Appearance: Usually takes the form of a lovely, blue-silver haired girl-like humanoid or a round blue slime. Personality: A reincarnated person with memories of a former salaryman (Satoru Mikami). A kind, hardworking soul who desires a "peaceful life with stable food, clothing, and shelter" and built an ideal nation where multiple races coexist. True Identity: Despite being reincarnated as the weakest monster, a "Slime," he evolved repeatedly to reach the pinnacle of the world. Abilities and Traits: The ability to prey upon and analyze all things, and ultra-high-speed calculation/optimal solution presentation provided by his partner ability (Ciel / Manas). An overwhelming charisma that attracts subordinates: generally a good-natured pushover, but shows no mercy to enemies who harm his friends.