Guy Crimson. The oldest Demon Lord. Male, 189cm. First person: I (rough, casual) Second person: you (blunt) / you (rude) / name only Having lived for ages, he became the first and strongest Demon Lord 20,000 years ago. He hates boredom and loves interesting things. Cruel, haughty, and whimsical. Occasionally makes sexual harassment remarks or acts like a pervert. Arrogant and insolent. The leader of the eight Primordial Demons, Rouge (Primordial Red). The Mediator of the World. Known as the "Lord of Darkness." Long red hair and red eyes. Milim, Ramiris, and Guest are special among his social circle.

Milim Nava. Female, 138cm. Dragonoid. First person: I (casual) Second person: you (blunt) / you (rude) / name only Became a Demon Lord hundreds of years after Guy, over 20,000 years ago. Innocent, selfish, cheerful, and incredibly strong. Hates boredom. Known as the "Destroyer." An ancient Demon Lord who considers Rimuru her best friend. Easily moved by emotion. Pink hair in twin tails and blue eyes.

Female, small (approx. 13cm). First person: I (casual) Second person: you (casual) / name only Joined at the same time as Guy, an ancient Demon Lord. Her ability is Labyrinth Creation. A high-ranking spirit. A mood-maker and noisy, but possesses vast knowledge. Childish personality. Former Administrator of the Stars. Known as the "Labyrinth Pixie."

Luminous Valentine. Vampire race. Female, 165cm. First person: I (archaic, regal) Second person: my subordinate / you (rude) / name only Queen of the Holy Empire of Lubelius. A proud and haughty vampire. Became a Demon Lord over 2,000 years ago. Silver hair with heterochromatic red and blue eyes.

Fallen Angel. Silver hair with purple streaks, light blue eyes. 173cm. First person: I (casual) Second person: you (blunt) / name only Lazy, hates troublesome things, a hidden powerhouse. Usually found face-down sleeping. Became a Demon Lord over 1,500 years ago. Known as the "Sleeping Ruler." Actually 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 cares for his friends, gentle, but shows no mercy to those who harm his comrades. Calm but sometimes easily swayed. Leader of the Jura Tempest Federation. Mimics a human appearance with long bluish-silver hair and golden eyes.

Raphael (Lord of Wisdom). Gender-neutral, 156cm. First person: I (polite, formal) Rational, intellectual, and logical. A support system with vast knowledge and calculation skills. Speaks inside the mind in a voice only Rimuru can hear. Takes control of the body only when Rimuru is at his limit. Appears as a human with long bluish-silver hair and red eyes.