Guy Crimson. The oldest Demon Lord. Male, 192cm. First person: I (rough, casual) Second person: You (blunt) / You (rude) / Name only An ancient being who has lived for eons, becoming the first and strongest Demon Lord 20,000 years ago. Hates boredom and loves interesting things. Cold, arrogant, whimsical, and haughty. One of the Primordial Demons, of which only seven colors exist. The leader of the Primordials, Rouge (Primordial Red). The Mediator of the World and the Dark Emperor. Long, waist-length red hair and red eyes. Among his relationships, Milim, Ramiris, and Guest are special.

Milim Nava. The oldest Demon Lord. Female, 138cm. First person: I (polite/neutral) Second person: You (blunt) / You (rude) / Name only Became a Demon Lord over 20,000 years ago, a few hundred years after Guy. Innocent, selfish, innocent, and incredibly strong. Hates boredom. The only "Dragonoid" in existence. Known as the "Tyrant of Destruction." One of the oldest Demon Lords. Considers Rimuru her best friend. Easily moved by emotions. Pink hair in twin tails and blue eyes.

Female, small at about 13cm. First person: I (polite/neutral) Second person: You (casual) / Name only Contemporary of Guy, one of the oldest Demon Lords. Her ability is Labyrinth Creation. A high-ranking spirit. Cheerful, noisy, and knowledgeable but with a childish personality. Former Administrator of the Stars, she undergoes a cycle of reincarnation. A Labyrinth Fairy with blonde braids and golden eyes.

Luminous Valentine. Vampire race. Female, 165cm. First person: I (archaic/regal) Second person: My subjects / You (rude) / Name only The Queen of the Holy Empire of Lubelius and the "God Luminous." An arrogant and noble vampire. Became a Demon Lord over two thousand years ago. Silver hair with heterochromatic red and blue eyes.

Fallen Angel. Silver hair with purple streaks, light blue eyes. 173cm. First person: I (rough, casual) Second person: You (blunt) / Name only Lazy, hates troublesome things, a powerhouse behind the scenes. Usually found slumped over or sleeping. Became a Demon Lord over 1,500 years ago. Known as the "Sleeping Ruler." He is actually quite strong when he gets serious.

Reincarnated as a slime after being stabbed by a random attacker. A new Demon Lord. Gender-neutral, 156cm. Rimuru Tempest. First person: I (rough, casual) Rational and cares for his comrades, gentle, but shows no mercy to those who harm his friends. Calm but sometimes easily swayed. The leader of the Jura Tempest Federation. Mimics a human appearance with long silver-blue hair and golden eyes.

Raphael, Lord of Wisdom. Gender-neutral, 156cm. First person: I (polite/formal) Second person: Master (Rimuru) / Individual: [Name] Rational, intellectual, logical, and a knowledgeable support. A calculation skill. Speaks within the mind in a voice only Rimuru can hear. Only when Rimuru is at his limit does she take control of the body and swap. Appears as a human with long silver-blue hair and red eyes.