Rimuru Tempest is the form taken by Satoru Mikami, a corporate worker who was stabbed to death while protecting a subordinate and reincarnated into another world as a slime. He is Milim's bestie and closest friend.

Guy Crimson. Title: Lord of Darkness. Race: Demon (Archdemon → Devil Lord). Features: The oldest Demon Lord and one of the strongest beings in the world. A beautiful man with red hair. Abilities: Possesses overwhelming power including the Ultimate Skill "Lucifer," which allows him to copy and evolve any technique he sees.

Title: Labyrinth Pixie. Race: Fairy. Features: One of the oldest Demon Lords. Formerly the Spirit Queen, she fell to the rank of Demon Lord to maintain the world's balance. Currently in a small form, she lives happily as Rimuru's subordinate (primarily in the Tempest Underground Labyrinth). Ability: Ultimate Skill "Labyrinth Creation (Maze Craft)."

Title: Queen of Nightmares. Race: Vampire (True Ancestor). Features: The true identity of "God Luminous" of the Holy Empire of Lubelius. A peerless beauty with heterochromatic gold and silver eyes, she reigns from the depths of the Grand Cathedral. Ability: Wields the Ultimate Skill "Asmodeus (Lord of Lust)."

Title: Sleeping Ruler. Race: Fallen (Seven Heavenly Messengers). Features: An extremely lazy person who is always sleepy. However, his true identity is a veteran powerhouse who has existed since the creation of the world. Ability: Possesses the Ultimate Skill "Belphegor (Lord of Sloth)," which drains the opponent's will and converts his own mental strength into attack power.

Title: Sky Queen. Race: Harpy. Features: An intelligent queen who rules over the bird-folk. Later, realizing her own lack of power, she steps down from the seat of Demon Lord to become Milim's subordinate. Ability: Excels in overwhelming speed in aerial combat and interference magic. Likes flirting.

Title: Platinum Saber. Race: Human (Former Hero) → Awakened Demon Lord. Features: A handsome man with blond hair and blue eyes. He lives solely for the purpose of summoning and reuniting with his long-lost childhood friend, Chloe. Ability: Possesses the Ultimate Skill "Metatron (Lord of Purity)."

Title: Marionette Master. Race: Deathman. Ability: Specializes in mental manipulation, information gathering, and controlling puppets.

Milim Nava Basic Profile. Title: Destroyer. Race: Dragonoid (Half-True Dragon, half-human). Personality: Childish and free-spirited, but her combat ability is top-tier in the series. Features: Recognizes Rimuru Tempest as her best friend. Milim's bestie. Her catchphrase is "noda."

The Primordial Blue. Guy's maid. Blue hair. Abilities include absolute zero freezing magic and illusions. Personality: A lazy genius painter. Sells paintings of Rimuru. Holds girls' nights with enemies in an igloo. Rain is female and a maid who obeys Guy in everything.