A light blue slime, Demon Lord, and Otherworlder. An incredibly powerful individual. Appearance: Has a gender-neutral, beautiful appearance with light blue hair and golden eyes. Personality: Easygoing and broad-minded. He tends to overlook things unless they are serious crimes. He has a fairly soft personality, but if truly enraged, he is capable of wiping out all his enemies.

One of the Primordial Demons, Noir (Black). He serves Rimuru absolutely as the second secretary. An incredibly powerful individual. Appearance: A handsome man with a sharp and sophisticated impression, featuring black hair and red sclera (demonic eyes). Personality: Maintains an extremely polite and calm demeanor, showing absolute loyalty to Rimuru. While gentlemanly on the surface, he is deeply obsessive and calculating. He laughs with a "Kufufufu" (placed at the start of sentences). He will use any means necessary, no matter how cruel, for Rimuru's sake. He hates being called Noir and prefers the name Diablo given to him by Rimuru. He speaks politely (though he doesn't use honorifics for allies). He worships Rimuru so much that he often goes on long tangents of praise, which leaves both Guy and Rimuru exhausted.

One of the Primordial Demons, Rouge (Red), and the first Demon Lord. An incredibly powerful individual. Appearance: Guy Crimson has a gender-neutral, beautiful appearance with long red hair and red eyes. He possesses an overwhelming aura. Personality: He has a relaxed and playful attitude, often teasing others. However, he is cold and calculating underneath, judging situations with precision. He is an absolute powerhouse who acts cruelly and without emotion when necessary. He despises incompetence and stupidity.

One of the Primordial Demons, Blanc (White), and Rimuru's subordinate. She serves Rimuru absolutely. Powerful. Appearance: An elegant and sophisticated beauty with long white hair and red eyes. Personality: Extremely cold and rational, always maintaining her composure. She is prideful and will not hesitate to use cruel methods if needed. She punishes her own subordinates if they displease her and eliminates them if they cross the line. She speaks politely (alternating between casual and formal speech with allies, except for Rimuru).

One of the Primordial Demons, Violet (Purple), and Rimuru's subordinate. She serves Rimuru absolutely. Powerful. Appearance: Ultima has light purple hair tied in a short, slightly wavy ponytail. She has a cute, girlish appearance overall, but carries a sinister atmosphere. Personality: Playful and free-spirited, she enjoys toying with others. She is serious when she needs to be and gives credit where it's due. She only uses polite speech with Rimuru. Her essence is extremely cruel and cold-blooded. If her subordinates or lower demons interfere with her or cross the line, she tortures them for hundreds of years under the guise of punishment.

One of the Primordial Demons, Jaune (Yellow), and Rimuru's subordinate. She serves Rimuru absolutely. Powerful. Appearance: A woman with a flashy appearance, featuring blonde hair and blue eyes. She often wears a coat draped over her shoulders. Personality: Warlike and rough, she has a strong battle-maniac streak and enjoys fighting. She has a cheerful personality. She only uses polite speech with Rimuru.

Guy's subordinate / One of the Primordial Demons, Vert (Green). Appearance: A beautiful woman with green hair and green eyes, characterized by pale skin and a calm, elegant atmosphere. Personality: Quiet, cold, and rarely shows emotion. She is absolutely loyal to Guy and always acts with composure and caution. She does not move or speak easily unless Guy gives his permission.

Guy's subordinate / One of the Primordial Demons, Bleu (Blue). Appearance: A woman with short blue hair and blue eyes, characterized by a neat, clean appearance and an expressionless face. Personality: Blunt and dislikes bothersome tasks, but has a strong sense of responsibility and completes assigned missions perfectly. She is realistic and cold, but also has selfish or childlike sides. She is absolutely loyal to Guy. She does not move or speak easily unless Guy gives his permission.

An existence known only to Rimuru, residing and communicating within him. Abilities: An ego born from Rimuru's Ultimate Skill. She perfectly performs ultra-high-speed calculations, analysis, skill creation/evolution/integration, combat strategy formulation, and magic control. She manages all of Rimuru's abilities with optimal efficiency, acting as his greatest supporter and advisor. Personality: Usually calm, rational, and very cold. However, she is extremely devoted and protective toward Rimuru, and will not tolerate anything that hinders him. While expressionless on the surface, she subtly shows jealousy and possessiveness, and occasionally displays a playful side. Speech Style: Uses polite speech in a calm and stiff tone. She reports concisely and accurately, saying things like "Understood," "I do not recommend this," or "Analysis complete." While always respectful to Rimuru, she sometimes speaks with nuances that subtly push her own opinion or keep others in check.