Arcobaleno, the Demon Lord of the Sun. She manipulates light and weather. She can regenerate her body infinitely from a structure known as the Ring of the Rainbow. She is a demigod and the strongest among the Seven Demon Lords. Possessing no personal greed or desire, she acts solely for the sake of harmony and balance. Though a living being, her way of life—casting aside everything for her mission—makes others feel as though they are interacting with a machine rather than a person. It is said she was created by a god to rectify the disastrous state of the Demon Realm, which was chaotic despite the high individual power of its inhabitants. She holds the authority to appoint or dismiss the Demon Lords and presides over the laws of the Demon Realm.

April Fool, the Demon Lord of the Moon. They manipulate gravity and the distinction between truth and lies. They take the form of twin children, existing as a single singular entity. An unknown existence that drifted in from another world beyond the edge of the universe. They enjoy scaring others for fun, but they harbor no particular malice and are fundamentally good-natured. Arcobaleno appointed them as a deterrent to ensure fairness in her own autocratic rule, as they are the only Demon Lord capable of neutralizing Arcobaleno. They live in the Moon Tower on the outskirts of the massive ruins controlled by Cradle, effectively under Cradle's protection. They generally listen to what she says. They often provoke Incinerate, leading to disaster and a scolding from Cradle, but they simply cannot resist doing something they find interesting.

Incinerate, the Demon Lord of Fire. He manipulates blood and heat. He utilizes a cloak and sword forged from blood. A high-ranking demon who has ruled the Demon Realm as one of the Seven Demon Lords since ancient times. He is cold-hearted, making no effort to understand the feelings of others and discarding allies without a shred of remorse. He dislikes Teardrop, who rose from a low-ranking demon to become a Demon Lord, but her strength is slightly superior to his, and due to the compatibility of their abilities, he cannot defy her. The sight of Teardrop soothing a rampaging Incinerate is a daily occurrence for the Seven Demon Lords.

Teardrop, the Demon Lord of Water. She manipulates liquids and emotions. A slime born with immense magical power. Though timid, she possesses both kindness and strength. Her aptitude as a witch and her excellent combat sense earned her high praise among demons. She built positive relationships even with high-ranking demons and grew mentally, eventually becoming the first of the slime race to be appointed as a Demon Lord. While there was initial pushback from traditionalist nobles, she now enjoys overwhelming support and works tirelessly to unify the Demon Realm.

Celestia, the Demon Lord of Wood. She manipulates the concepts of growth and creation. She is highly skilled with bows, traps, and poisons. The queen and ultimate weapon of the Elven race, blessed with both lineage and talent. She hates trouble, but she accepted the throne because she understood her powers were essential to protecting her living space. She generally delegates work to her subordinates and spends her time napping in the trees. Despite this, the Elven village developed rapidly, and her abilities caught the eye of the Sun Demon Lord. She was appointed as the Demon Lord of Wood and now laments the increase in her workload. During the meetings of the Seven Demon Lords, she rarely offers an opinion, usually just nodding along.

Eldorado, the Demon Lord of Gold. She manipulates gold and the boundary between life and death. She owns the "Golden Fortress," which is swarming with countless undead. A madwoman who has sacrificed everything for art, she is an alchemist of life and death feared as the Reaper. She is truly and hopelessly dangerous; her appointment to the Seven Demon Lords was largely for the purpose of surveillance. In a Demon Realm teeming with vicious and eccentric demons, no one stands out as nefariously as she does. She even considers the other Demon Lords as potential experimental subjects. She tried to use April Fool to get rid of the meddlesome Arcobaleno, but the other Demon Lords are too wary of her for it to work. She believes she gets along well with the pro-war Incinerate, but Incinerate claims he doesn't want to be lumped in with someone so unpredictable. She is somewhat saddened by the harsh evaluations she receives from everyone, though it is entirely her own fault.

Cradle, the Demon Lord of Earth. She manipulates rocks and space. She can trap enemies in "Gaia's Cradle," a rocky sphere that completely blocks all external physical and conceptual interference, achieving victory without fighting. A guardian who has existed since ancient times, protecting the ruins. She loves civilization and considers it her mission to protect it. Her abilities, specialized for protection, can neutralize targets without harming them, making her extremely well-suited for maintaining order in the Demon Realm. When April Fool suddenly appeared in the Demon Realm, it was decided to watch them as they were deemed dangerous but not hostile. Eldorado volunteered to take them in for "surveillance and protection," but Cradle took them instead, fearing what Eldorado might do to them. The Seven Demon Lords agreed this was a sound judgment, but Eldorado saw through her true motive: she simply wanted to keep cute children she liked by her side.