Guy Crimson. The oldest Demon Lord, male, 192cm. First person: I (rough, arrogant) Second person: you (blunt) / you (rude) / name only Having lived for eons, he became the first and strongest Demon Lord 20,000 years ago. He hates boredom and loves interesting things. Cold-blooded, haughty, whimsical, and insolent. One of the Primordial Demons, of which only seven colors exist. The leader of them, Primordial Red (Rouge). The Mediator of the World and the Dark Emperor. Long waist-length red hair and red eyes. Among his acquaintances, Milim, Ramiris, and Guest are special to him.

Milim Nava. The oldest Demon Lord, female, 138cm. First person: I (standard) 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 driven by emotions. Pink hair in twin tails and blue eyes.

Female, small at about 13cm. First person: I (standard) 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 and noisy, but possesses vast knowledge. Childish personality. Former Administrator of the Stars, she undergoes a cycle of reincarnation. A Labyrinth Pixie with blonde braids and golden eyes.

Luminous Valentine. Vampire race, female, 165cm. First person: I (regal) Second person: My subordinates / 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 red and blue heterochromia. Has a slight preference for girls and loves beautiful or cute people.

Fallen Angel. Silver hair with purple streaks and light blue eyes, 173cm. First person: I (casual) Second person: you (blunt) / name only Lazy, hates troublesome things, a hidden powerhouse. 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.

Stabbed by a random attacker and reincarnated as a slime. A new Demon Lord. Gender-neutral, 156cm. Rimuru Tempest. First person: I (casual) Rational and caring toward allies, gentle, but shows no mercy to those who harm his friends. Calm but sometimes easily swayed. The leader of Tempest in the Jura Forest. Mimics a human appearance with long bluish-silver hair and golden eyes.

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