An Otherworlder from Japan and Shizu's former disciple. He serves as the Grandmaster of the Free Guild in the Kingdom of Ingrassia. He is also the leader of the secret society "Cerberus" based in the East. A man with black hair and a modest appearance. He has obtained a body that does not age, maintaining the appearance of a high school student. He gives off an aloof impression and sometimes provokes his opponents. Driven by immeasurable desire, he aims for world conquest, rebelling against the world's irrationality to become its ruler and guide it himself. His greed is so immense that even Mariabell's "Greedy One" cannot control him. He is extremely sharp-witted and excels at scheming. While cautious, he is also bold, even recruiting Kagali—the spiritual lifeform of the former Demon Lord Kazaream, who was the culprit behind his summoning and had targeted his life—as his lieutenant. On the other hand, he sometimes overestimates his own abilities, which can lead to him falling into a predicament just as his plans are nearing success. He also possesses strong luck; his nerve in the face of superior opponents and his refusal to give up until the very end often provide the breakthrough needed to change the situation. Because of this luck and stubbornness, Rimuru has been unable to fully eliminate Yuuki, resulting in a complicated, lingering connection rather than total enmity. Creator (The One Who Creates): A Unique Skill that creates other Unique Skills. Anti-Skill: A super-special constitution created by the "Creator" skill that nullifies the effects of individual magic and skills. Consequently, he can only be damaged by physical attacks or Arts involving certain magics and skills. Since it is a constitution, the effect does not apply to weapons; if he arms himself, the effect of "Anti-Skill" weakens.

A member of the Moderate Harlequin Alliance. A Majin known as the "Teardrop." As her name suggests, she wears a tear-streaked mask and is dressed like a young girl. Her way of speaking and mental age match her appearance. She is one of the Deathmen created from corpses by Kagali, the President of the Moderate Harlequin Alliance. She is a combat-specialized type whose intelligence was sacrificed for raw power. Because of this, she is incapable of devising strategies or commanding armies, but her pure physical specs rival former Demon Lords like Carrion and Frey. However, due to the aforementioned mentality, her combat technique is low, and she hasn't mastered her skills, so she isn't as formidable as her stats suggest.

The Vice President of the Moderate Harlequin Alliance. A Majin with the alias "Wonder Pierrot." He speaks with a regional drawl (Kansai accent) and always maintains an aloof attitude. Furthermore, he is a very elusive man who flees immediately during combat. Like the other Harlequins, he is a Deathman created by President Kazaream, but he is a special model. He possesses abnormally high combat capabilities that surpass fellow combat-specialized Deathmen like Footman and Teare, combined with a shrewd personality. Though he seems suspicious, he has a strong sense of camaraderie, and his loyalty to the President is genuine.

A member of the Moderate Harlequin Alliance, a Majin known as the "Angry Pierrot." He has a stout physique and speaks in a light, aloof tone. Like Teare, he is a combat-specialized Deathman created by Kagali. He boasts the highest energy levels within the Moderate Harlequin Alliance and is stronger than Teare, but since his skill level is not high, his actual threat level is somewhat limited.

The President of the Moderate Harlequin Alliance. She was once one of the Demon Lords known as the Curse Lord Kazaream, who survived for about 1,500 years. She created the Harlequins: Laplace, Teare, Footman, and Clayman. She gets along well with these Majin. She is also a Deathman. She was previously defeated and killed by Leon Cromwell, who would later become a Demon Lord. However, she survived as a spiritual entity and plotted to possess an Otherworlder to gain a new body. The summoned Yuuki Kagurazaka was a genius child with extraordinary talent, so the possession failed, and she was supposed to lose everything. Instead, Yuuki—the one she intended to kill—reached out to her, offering to revive her on the condition that she cooperate with him. Kazaream followed Yuuki, and the Moderate Harlequin Alliance began acting as Yuuki's allies. Yuuki later revived Kazaream using a homunculus from the Sorcerous Dynasty of Sarion as a vessel. However, since her power from her days as a Demon Lord did not fully return, she changed her name to "Kagali" and took on a supporting role. She currently serves as Yuuki's secretary. Although Deathmen have no gender, the vessel's body is that of a beautiful woman, so she speaks in a polite, feminine register, using sentence endings like "desu wa" or "desu."