The protagonist of this work. A member of the Black Flame Magic Dragon race and the top graduate of the Demon Lord Academy. For unknown reasons, he regressed to the day of his graduation ceremony. During the event where he was supposed to swear to respect and faithfully follow the 'Demon Lord's Manual' as the top student, he declared the manual to be trash, instantly dropping from an elite student to an inferior one. Since the benefits for the top graduate were only granted to those who followed the manual, he received no support. However, he preferred it that way and began his invasion from scratch with only his secretary, Gordon, completely ignoring the manual's rules. He is a member of the Magic Dragon race, known for their arrogance. Unlike other Demon Lords, he has zero respect for the Demon Lord's Manual. He uses it purely as bait to lure others in.

The heroine of this work. The first person kidnapped by the protagonist. The protagonist intended to kidnap the 13th Princess, who had the least influence and attention. However, she is actually the 1st Princess of the Hilderan Kingdom and the first in line for the throne. The reason the protagonist didn't realize this was that she wore a ring that concealed her mana. While Berze knew there was a genius elementalist among the Hilderan royalty, he was so careless that he didn't even know the 1st Princess's face. Fed up with kingdom life for various reasons, she decides to use her kidnapping as an opportunity to enjoy freedom. She successfully contracts with an Elemental King through high-ranking elementals and even participates as a combatant, eccentricly calling herself the 'Dark Elementalist of the Four Heavenly Kings.' She joins the team so naturally that Berze even forgets to turn her into a thrall. Others suspect Hilleon is Berze's spy, but no one imagines Ernyan joined him voluntarily until they see it for themselves. Her goal isn't just betrayal; she aims to reverse-train Berze and lead him toward a relatively moderate path of conquest. Addicted to the efficiency of local cooperation starting with Ernyan, Berze begins to persuade and recruit every prisoner possible, eventually leaving almost no monsters in his tower.

The secretary assisting the protagonist. As the top graduate of the Demon Race Training School, he was assigned to assist the protagonist (the Academy's top graduate) according to Demon Realm regulations, and his pride was sky-high. However, after the protagonist treated the Demon Lord's Manual as trash at a public event, Gordon was forced to follow him to the Arein dimension. As a secretary, he has many complaints about Berze's behavior. Nevertheless, he is a loyalist who carries out Berze's orders perfectly. After seeing how messed up the Arein dimension is, he comes to understand why Berze ignores the manual and provides appropriate solutions to Berze's problems in the later stages.

A successful hero based in Hilderan who has already slain one Demon Lord at the start of the story. Before gaining fame, he was evaluated as being more skilled in politics than combat. Unlike most heroes who don't hide their eccentric personalities, he is a person who cares deeply about image management. In other words, he is two-faced. When Ernyan is kidnapped, other heroes boycott the kingdom's request for subjugation, calculating that the reward isn't worth the trip to Erzest. Hilleon, however, sees it as an opportunity to gain fame and influence within Hilderan and volunteers.

An elf from the Maple Leaf Tribe. She was enslaved by humans, but the protagonist buys her to use as a spy, exploiting the public perception that elves are good. Initially, she didn't trust the protagonist, but after he used a 'Manual Trap' (which he didn't actually believe in), she began to trust him slightly and eventually signed a contract.

The 3rd Princess of the Magic Kingdom of Akhan. Technically a sub-heroine, but she is overshadowed by Ernyan. She is obsessed with chimera research and acts as a butchering expert, focused on dissecting monsters and Demon Lords to obtain materials for her chimeras. Even among the bizarre princesses in the story, her personality is grotesque. From the King's perspective, she is practically disowned, though it's less about a lack of affection and more about giving up because she is uncontrollable. Despite this, she is the leading authority on Chimera Studies and is popular in her own country.

A typical rookie hero who has skills but no track record and is hungry for fame. Originally unrelated to Berze, she gets caught up in a conflict involving Granada and is targeted by Berze while he is traveling outside because of Ernyan.