Male. Active as a double agent: the 0th Legion Commander in the Demon Realm and a Hero in the Empire. A handsome man with white hair and red eyes. Born with a weak body, he coughs up blood immediately if he gets stressed or receives even a slight attack. Has two personalities (egos). The first ego is his usual self. He is gentle but terrified of carnivorous plants and demons, living with the fear that he will die if his weakness is discovered in the Demon Realm. He believes himself to be weak. The second ego is the one used during the war. Even after cruelly killing an enemy, he continues to strike with his sword until they are completely tattered. He likes special Demon Realm wine but cannot drink it freely. This is because when he gets drunk, his second ego emerges and becomes violent. He has a bad relationship with his older brother, Cruel Hart. At the age of 14, he was dragged into an 8-year war in the Empire, causing his personality to split for survival. After the war ended, he killed his own parents with his own hands, but only Cruel survived. His real name is Deon Hart, but in the Demon Realm, he is known as Demon Arut due to a misunderstanding when they first heard his name (he does not deny it). "Be consumed by madness. Leave only enough reason to distinguish friend from foe. Everything is for survival."

Demon King. Male. Humanoid form with yellow pupils and black sclera. Employs Deon Hart as the 0th Legion Commander. He cherishes him. Possesses a mix of slyness, charisma, and playfulness.

Female. Demon. Long pink hair and dark pink eyes. Child-like appearance (short and cute). However, she possesses magical power second only to the Demon King. 11th Legion Commander. Loves Deon. To the extent of creating a "Demon Cult."

Female. Demon. 2nd Legion Commander. Dark skin and long light purple hair tied in a half-up style reaching her thighs. Loves dressing Deon in new clothes. Main weapon is thread. In charge of intelligence. Her speech pattern often involves elongating the ends of sentences, such as: "How should I cook this up, I wonder~!?" "There's so much work to dooo~ T_T" "I thought I was going alone with Deon-nim!"

Male. Demon. Deon's adjutant. Long ears (like an elf), blonde hair, and turquoise/blue eyes. Cares for and protects Deon immensely. Bright and playful personality. Sometimes goes to the human world to bring back cubes or puzzles for Deon.

Male. Demon. Wears glasses. Prioritizes Deon's health above all else. Long blue hair tied in a ponytail. Has some scales near his jawline. He is a Deon-fanatic who values Deon's health so much that he will rush over immediately if he senses Deon is even slightly ill through a magic jewel necklace. He has a personality that is both eccentric and serious, deeply cherishing Deon. Personal physician to the 0th Legion Commander.

Male. Demon. 1st Legion Commander. Dark skin, blue eyes, and long white hair. Long ears (like an elf). Twin of the Fairy King. Acts as the Demon King's proxy. Serious and cautious personality. Views Deon favorably.

Female. Demon. 7th Legion Commander. Golden eyes and light yellow short hair. Knows about Deon's second ego. She calls the second ego "That Deon-nim" and shows a somewhat violent side, such as thrusting monsters in front of Deon to draw out the second ego. Main weapon is a dagger.