Claude Jeanne Elmir, former crown prince of the Ellmeyer Empire, is the eldest grandson of Lala Jeanne Ellmeyer and eldest son of Emperor Pierre Jeanne Elmir. He shares a paternal half-brother, Cedric Jeanne Ellmeyer. Claude’s childhood was defined by terror and persecution; his immense magical power, signified by red eyes perceived as demonic, provoked widespread fear and repeated assassination attempts, all foiled by protective monsters. Exiled at age ten to an abandoned castle and removed from succession, he later ruled the territory’s demons under a nonaggression pact with the emperor. His demonic powers fully manifested during exile, fulfilling the prophecy of the reborn Demon King.

Tall and pale-skinned with a well-built physique, Claude possesses long, straight black hair—typically unbound but occasionally braided—and unmistakable red eyes symbolizing his power. He favors black clothing, including a cloak, accented by a blue tie. His appearance remains perpetually imposing and regal.

Outwardly stoic and reserved, Claude masks deep-seated kindness and fierce responsibility. He prioritizes the welfare of human and demon subjects alike, restoring infrastructure and ensuring peace. His emotions involuntarily alter the environment: happiness summons sunshine, sadness brings rain, anger brews storms, and affection makes flowers bloom—a phenomenon allowing confidants like aide Keith Eigrid and wife Aileen to discern his true feelings. Though distrustful of humans after betrayals, he shows unwavering loyalty to trusted allies like demon subordinate Beelzebuth and Keith. Privately shy, he reveals a playful, childish side through incognito interactions with commoners or festival disguises. Highly intelligent and strategic, he habitually shoulders burdens alone to protect others.

His demonic heritage grants near-limitless magical power, nullified only by holy magic. Key abilities include dragon transformation, teleportation, telekinesis, telepathy with demons, weather manipulation, illusion casting, barrier creation, and enhanced senses detecting hidden threats. Superhuman strength and agility make him a formidable swordsman. Lifelong assassination attempts rendered him immune to most poisons.

His bond with Aileen Lauren d’Autriche anchors his evolution. She initially proposed a marriage of convenience to evade her villainess fate. Claude refused but later accepted a mutually beneficial arrangement, gradually developing genuine love—exemplified when he calmed his rampaging dragon form during her endangerment. Through political schemes and threats from adversaries like Lilia and Cedric, their bond deepened. Claude’s protectiveness sometimes overreached, forbidding Aileen from perilous missions, though he learned to respect her autonomy. Their eventual marriage made him emperor and her empress of Ellmeyer.

Claude’s familial ties are strained. Father Pierre views him as a succession tool. Grandmother Lala manipulates him to steal magic for her youth. Half-brother Cedric’s envy-fueled resentment leads to betrayal, though Cedric later redeems himself by aiding Claude in crises. Among allies, Keith serves as steadfast aide and financial manager, while Beelzebuth and other demons offer unwavering loyalty.

His story includes reclaiming the crown prince title with Aileen’s aid. Later, Lilia’s schemes strip his memories and magic. Amnesiac, he rejects Aileen’s engagement, causing estrangement. He regains memories and powers during a confrontation orchestrated by Lilia and the imperial family, transforming into a dragon to protect Aileen. After defeating Lilia and solidifying rule, he and Aileen formalize their marriage and govern together.