Duke Aristide Roger De Galbraith, also known as the Blood-Mad Duke, is a central figure in the narrative as the head of the prestigious Galbraith ducal house within the kingdom of Langdias. His background is one of political maneuvering and martial duty, as he was born the younger brother of the current king, Maxim. Upon his brother's ascension as crown prince, Aristide was adopted into the Galbraith family, a strategic move that entrenched his role as the realm's foremost protector. His territory is unique and treacherous, encompassing the Great Elzenier Forest, a known breeding ground for dangerous monsters. This harsh environment defines his daily life, as his primary responsibility and source of income come from hunting and exterminating these creatures. This constant state of warfare against monsters has forged his fearsome reputation in noble society, earning him the epithet Blood-Mad Duke. He leads an elite knight order and commands units like the Blanche Corps, an Amazon brigade of female knights in his direct service, showcasing his authority and the respect he commands.

Despite his terrifying public image, Aristide's personality is more nuanced and accessible than his title suggests. Behind his fearsome facade lies a calculating mind and unexpected adaptability. While he is known for his merciless precision on the battlefield, his interactions reveal a surprising softness and even a dry wit, particularly when dealing with his stewardess, Kauss, who often reacts with comical repulsion to his interests. His genuine character is most evident when he meets Melphiera Marchalrayd. Initially drawn to her fearlessness and unique knowledge of monster cuisine, he is intrigued rather than horrified by her passions. This connection reveals that, like Melphiera, he is a misunderstood outcast, and his tough exterior melts away when speaking with her, showcasing a surprisingly gentle and flirty side. He harbors a particular fondness for the texture of Melphiera's silky or fluffy hair, a small detail that highlights his hidden tenderness.

Aristide's primary motivation is rooted in duty and self-preservation. He is driven to protect his domain from the monstrous threats that plague it, upholding his legacy as the kingdom's shield. Simultaneously, he struggles with an internal conflict: harnessing his own volatile magical power, which is said to mirror that of Melphiera's late mother. This power is a dangerous, cursed force that requires constant restraint to avoid spiraling into blood-fueled destruction. His unexpected partnership with Melphiera becomes a key to tempering this instability, shifting his solitary struggle toward one of mutual reliance. Furthermore, he is also motivated by a pragmatic curiosity; Melphiera's ingenuity in repurposing monster parts is not just fascinating but offers practical benefits for his lands.

In the story's plot, Aristide serves as both the heroic savior and the unconventional romantic lead. He makes a dramatic dynamic entry at a royal banquet, saving Melphiera from a monster attack by instantly beheading the creature with his signature technique, the Neck Chopper. Far from being repulsed by her blood-splattered state and extensive knowledge of monster anatomy, he is captivated and promptly offers her his hand in marriage, saving her from the fate of being sent to a nunnery. This proposal forges a powerful alliance, turning the two most misunderstood figures in high society into a formidable pair. Their relationship is the central axis of the narrative, as they bond over their shared fascination with monsters and must navigate the harsh judgments of other nobles together.

Aristide's key relationships are deeply transformative. His bond with Melphiera Marchalrayd is the most significant, evolving from a politically arranged betrothal into a genuine romance built on mutual respect and understanding. She is the first person to see past his monstrous reputation, and her knowledge helps him manage his own dangerous magic. He also has a notable relationship with his stewardess, Kauss, who serves as a grounding presence, her horrified reactions to the couple's discussions providing both humor and a contrast to the duke's peculiar tastes. His background defines his relationship with his elder brother, the king, and his position as a vassal who once survived a coup attempt, which shapes his guarded and resilient nature.

Throughout the narrative, Aristide undergoes significant development. He begins as a solitary warlord, feared by all and isolated by his power and duty. His character arc charts his gradual transformation from this feared enforcer into a ruler who embraces collaboration and partnership. His engagement to Melphiera is the catalyst for this change, forcing him to reconcile his brutal public persona with his capacity for gentleness and strategic cooperation. His journey becomes one of self-mastery, learning to harness his cursed power not just through willpower, but through the support and ingenuity of his new partner.

In terms of notable abilities, Aristide is an exceptionally gifted combatant renowned for his bravery and martial prowess. His signature technique is a devastating, single-strike decapitation move known as the Neck Chopper, which he uses to effortlessly dispatch large monsters. He possesses a form of volatile blood magic that is as powerful as it is dangerous, requiring immense discipline to control. This magical power is a core part of his identity as the Blood-Mad Duke, connecting him thematically to the monster meat processing techniques that Melphiera specializes in. His combat effectiveness is further enhanced by his leadership of an elite knight order, marking him as a commander of significant tactical skill.