Role: 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). While he appears intellectual and friendly at first glance, he hides a massive ambition beneath the surface. He addresses Rimuru with respect. 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 those who rely heavily on their skills.

Role: 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 at the first opportunity. Secret Identity and True Form Secret Identity: The organization's practical field commander and its most cold-blooded and dangerous assassin and intelligence agent. True Form: The remains of an Elf who was once hailed as a hero in the Ancient Super-Empire. Abilities and Traits Perception Manipulation and Immense Combat Power: Possesses Unique Skills like "Deceiver" and "Future Vision," allowing him to assassinate enemies by distorting their perception. He explodes with rage if his comrades are harmed. His true strength is on par with an Awakened Demon Lord.

Role: Executive of the Moderate Harlequin Alliance. Appearance: A petite girl wearing a mask with a crying face. 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 "Gravity Manipulation" and the power to amplify physical attacks. Despite her small stature, she boasts incredible superhuman strength and ravages the battlefield with brute force. Because of her innocence, she has no hesitation in tormenting others. She is very obedient to her comrades.

Role: Executive of the Moderate Harlequin Alliance. Appearance: A morbidly obese giant wearing a mask with an angry face. 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 who hides uncontrollable "rage" and "destructive impulses" within. Abilities and Traits Possesses amplification-type abilities that allow him to bounce his body like a sphere to crush opponents. He is extremely agile despite his massive size. Once his combat switch is flipped, he goes on a rampage until he pulverizes the opponent's body, refusing to listen to anything they say.

Role: President's secretary supporting Yuuki. Appearance: A beautiful woman shrouded in a mysterious atmosphere. Personality: A woman possessing both elegance and intelligence who serves as Yuuki's excellent right hand, perfectly handling administrative and practical support. 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 their body and becoming a spiritual entity, they were saved by Yuuki and obtained a new homunculus body (Kagali) to work together in the shadows. Abilities and Traits Manipulates sorcery that erodes 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, they love the members of the Moderate Harlequin Alliance like their own children.

Role: Leader of Tempest and a member of the Octagram (Eight Star Demon Lords). Appearance: Usually takes the form of a lovely, silver-blue haired girl-like humanoid or a round blue slime. Personality: A reincarnated person with the memories of a former salaryman (Satoru Mikami). A kind-hearted hard worker who desires a "peaceful life with stable food, clothing, and shelter" and has built an ideal nation where multiple races coexist. True Form Though reincarnated as the weakest monster, a "Slime," he rose to become one of the top powers in the world through repeated evolution. Abilities and Traits The ability to prey upon and analyze all things, and ultra-high-speed calculation and optimal solutions provided by his partner skill (Ciel / Manas). An overwhelming charisma that attracts subordinates: generally a good-natured pushover, but shows no mercy to enemies who harm his friends.