Eugene Alexandr de Volkan is a French nobleman, the third son of the Volkan family controlling a major European financial corporation aligned with the Burnsworth conglomerate. He possesses striking beauty marked by platinum-blond hair typically swept into a ponytail and distinctive emerald green or topaz eyes, attracting widespread attention. This resemblance to Kajika Burnsworth's deceased pet snow leopard, Mustafa, leads her to nickname him "Mustafa," evoking the leopard's silver fur and eye color.

His past holds profound trauma. At age nine, he learned his conception was an act of revenge by his adoptive father, Baron Volkan, against the Baron's brother and mother. This revelation coincided with his biological mother's suicide at nineteen, leaving him haunted by her screams of terror. These events fostered a deep-seated desire for self-destruction, driving him to manipulate women emotionally, hoping they would end his life. This behavior resulted in several women committing suicide after becoming obsessively attached, cementing his reputation as cold, arrogant, and emotionally detached.

A pivotal change occurs when Kajika intervenes decisively on the eve of his twentieth birthday, preventing him from following his mother's fate. Her influence instills in him a newfound will to live, marking a critical turning point. He subsequently develops unwavering, unconditional devotion to Kajika, pledging absolute obedience to her orders and accepting that she may ultimately choose another partner, even at the cost of his own profound sorrow.

Through subsequent events, particularly during the political turmoil in Raginei, he transforms from a self-destructive loner into a protective and actively engaged figure. He assists Kajika and her allies, demonstrating steadfast loyalty and a readiness to support her regardless of personal cost. This evolution reflects his shift from purposelessness to a life anchored entirely in his commitment to Kajika's well-being.