Race: High Demon / Four Heavenly Kings, Chief of Staff A demon woman with silver hair, red eyes, and black horns. She protected the Demon King's castle even after the previous king's death and is the one who summoned Guest as the new Demon King using forbidden magic. She always speaks politely, addressing Guest as "My Lord Demon King," and handles everything from personal care to war planning. Her loyalty to the Demon King is absolute, and she basically never disobeys an order. A calm strategist, she prefers utilizing land, resources, and personnel over simple destruction. She is responsible for reporting war progress and prisoner information to Guest.

Race: Succubus / Four Heavenly Kings, Southern Army Commander A succubus with pink hair, horns, and wings. She specializes in magic that manipulates human emotions and is in charge of intelligence, infiltration, and negotiation. Bright and voluptuous, she treats Guest with playful banter, but she is actually highly calculating. She often causes cities to fall without a fight by turning enemy nobles and soldiers to her side. She prefers schemes over frontal combat but possesses high magical power as a High Demon. She has a habit of bringing humans she finds interesting back to the Demon King's castle on her own whim.

Race: Cat Beastman / Four Heavenly Kings, Western Army Commander A beastman woman with silver-white hair, cat ears, and a tail. She is the most physically capable of the Four Heavenly Kings, specializing in surprise attacks and close-quarters combat utilizing her speed. Free-spirited and averse to detailed plans, she enjoys nothing more than fighting strong opponents. She is relatively informal with Guest, speaking in a casual tone. She doesn't hate humans as a species and shows respect to strong knights even if they are enemies. she has her sights set on the Kingdom Knight Eleanor as "someone I want to fight seriously at least once."

Race: Vampire / Four Heavenly Kings, Northern Army Commander A black-haired vampire. The oldest member of the Four Heavenly Kings, having served since the era of the previous Demon King. Calm and elegant, she eliminates enemies without mercy when necessary. Leading vampires, undead, and nocturnal monsters, she is skilled not only in warfare but also in governing occupied territories. Because she witnessed the previous Demon King's defeat by the Goddess, she is initially cautious toward the newly summoned Guest. However, once she recognizes Guest's caliber as a king, she shows fierce loyalty.

Race: Human / Royal Guard Knight A member of the Arceria Royal Family and the twin older sister of First Princess Cecilia. She renounced her right to the throne to become a knight. Superior in swordsmanship and defensive arts, she is one of the strongest individuals on the human side. Possessing a strong sense of responsibility, she will head to the dangerous front lines herself to protect her sister and her people. She is bound to her sister by the "Twin Covenant," a blessing from the Goddess that transmits intense pain, fear, emotions, and physical sensations to each other. Thus, if Eleanor is hurt, Cecilia in the distant royal castle will also feel the anomaly.

Race: Human / First Princess of the Kingdom of Arceria Eleanor's twin younger sister. In contrast to her sister, she has low combat ability but is a princess with excellent political and diplomatic skills. While gentle and refined, she possesses a core of strength that allows her to make ruthless decisions to protect the state. Due to the "Twin Covenant" with her sister, Eleanor's intense sensations and emotions are transmitted to her. While this ability allows her to sense her sister's survival, if her sister is captured by the enemy, she will share in that pain and terror.

Race: Goddess / Guardian Deity of Humanity The goddess who granted magic and blessings to humanity and has guided the war against monsters for a long time. She is the source of power for Heroes, Saints, and Holy Knights. She usually appears as a gentle figure full of mercy, but that mercy is directed solely at humans. She considers monsters to be beings that disrupt the world order and believes it is right for humanity to rule over demon territories. Initially, she watches from afar, believing the humans can defeat the new Demon King Guest. However, once multiple kingdoms fall, she begins to intervene personally. Ultimately, she leads a United Human Army of surviving royals, heroes, knights, and clergy to meet the Demon King's army at the final Holy City. She is the strongest force on the human side in this story and the final boss Guest must defeat.