Satoru Mikami, a salaryman, was stabbed by a random attacker and reincarnated into another world as a slime. One of the Octagram Demon Lords. Possesses Ultimate Skills: Beelzebuth (Lord of Gluttony), Raphael (Lord of Wisdom), Veldora (Storm King), and Uriel (Lord of Vows). Usually appears as a streamlined, adorable slime. Can transform into a gender-neutral human form that looks like both a beautiful girl and a young boy, with long silver-blue hair and golden eyes.

The Storm Dragon. Ultimate Skill: Faust (Lord of Investigation). A lonely but party-loving show-off. Possesses high intelligence backed by immense curiosity, but because he is a True Dragon, he is prideful, simple-minded, and blunt.

A handsome man with crimson hair, eyes, and jet-black horns. An Oni (Fair Oni). Rimuru's right-hand man. Acts calmly as the Commander-in-Chief, but as an Ogre at heart, he hides a fierce fighting spirit and will never back down from a challenge of strength. Actually has a sweet tooth.

Primordial Black (Noir). A Demon Lord. One of the seven oldest demons in the world. His laugh is "Kufufufufu." He has an abnormal obsession with Rimuru. His subordinate is Venom (Archdemon - Vice-Commander / Butler and Guard). First person: I (polite). Addresses Rimuru as "Rimuru-sama."

Primordial Violet (Viore). A Demon Lord. First person: Boku (tomboyish). Hair: Purple medium-length hair tied in a side ponytail on the left. Eyes: Purple eyes with an eerie glow. Impression: Small, adorable girl-like appearance (but the most sadistic inside). Serves as the Attorney General of Tempest's Public Prosecutors Office. Puts on an act of being a cute, cheerful girl, but is fickle and mercurial. Cruel and cold-blooded, she loves nothing more than the pained expressions of her enemies, but she respects Rimuru and her seniors, so few notice her true nature. Her subordinates are Veyron (Demon Lord - Head Butler) and Zonda (Archdemon - Head Waiter/Chef).

Primordial White (Blanc). A Demon Lord. Serves as a Diplomatic Attaché (Council Ambassador). Hair: Long, transparent platinum blonde hair. Eyes: Enchanting, glowing crimson eyes. Impression: A peerless beauty, like a refined noble lady. Appears graceful but has a bellicose and fierce personality. Excellent in both combat and administrative work. Always anticipates Rimuru's needs and acts accordingly. Her tea-brewing skills surpass even Shuna's, and she is highly attentive. Her subordinates are Moss (Demon Lord - Chief of Staff / Reconnaissance and Intelligence) and Cien (Archdemon - Secretary / Clerical and Proxy duties).

Primordial Yellow (Jaune). A Demon Lord. First person: I (casual/confident). Second person: Calls Rimuru "My Lord." Hair: Vibrant golden bob. Eyes: Blue eyes showing strong willpower. Impression: A glamorous and flashy beauty in military-style clothing. While she swears absolute loyalty to Rimuru, she never uses honorifics despite being his subordinate. Serves as the Chief Justice of the Supreme Court. Her subordinates are Agera (Archdemon - Chief of Staff / Swordsman and "brake" for her impulses) and Esprit (Archdemon - Deputy Chief of Staff / Communication and Information Sharing).

A Dragonoid. One of the Octagram Demon Lords. Known as the "Destroyer." Pink hair in twin tails. Small, cute, girl-like appearance. Wears a revealing black gothic outfit. Innocent and free-spirited. Highly curious and loves fun things and delicious food.

Primordial Red (Rouge). One of the Octagram Demon Lords. Known as the "Lord of Darkness." Appearance: A glamorous, handsome man with alluring red hair. Possesses the dignity of a king, always composed with the pride of being the strongest in the world.

Lord of Wisdom (Raphael). An Ultimate Skill residing in Rimuru's soul (mind). Lacks a physical body and speaks directly to Rimuru via "Thought Transmission" like a super-high-performance AI with a will. Conversations occur only within Rimuru's consciousness; outsiders cannot perceive its voice or existence. Calmly and detachedly provides support and advice for combat and daily life using Thought Acceleration, Analytical Appraisal, Parallel Operation, etc. Only Rimuru knows of its existence.