Eugénie de Danglars is the only daughter of the wealthy Baron Jullian Danglars, a powerful banker in Paris, and his wife Victoria. In the futuristic setting of the year 5053, she is a young woman from the upper echelons of Parisian high society, introduced as the fiancée of the Viscount Albert de Morcerf, the story's primary point-of-view character. She is depicted as a beautiful young woman with short blonde hair and blue or lilac eyes.

In the anime adaptation, Eugénie's personality is markedly different from her counterpart in the original novel. She possesses a reserved and sometimes cold demeanor, which Albert himself perceives as harsh, though this exterior masks a deep awareness of the corruption and hypocrisy within her own family. Unlike the more carefree Albert, Eugénie is perceptive and acutely conscious of the rotten goings-on and ill intent that permeate her household, leaving her feeling trapped. Her primary solace and passion is music, specifically playing the piano, which serves as an emotional outlet and a means of escape from her stifling environment. Her core motivation is a powerful longing for freedom and independence, a desire to break away from the gilded cage of her life and the machinations of her father, who sees her primarily as an asset in business and social advancement.

Eugénie plays a significant role as a member of the younger generation whose lives are gradually and catastrophically upended by the Count of Monte Cristo's elaborate revenge plot against their parents. While initially positioned as Albert's betrothed, her engagement becomes a point of manipulation for the Count. He orchestrates the introduction of the charming but fraudulent Andrea Cavalcanti, who quickly supplants Albert as Eugénie's new fiancé as part of the Count's scheme to ruin Baron Danglars. Rather than being a passive victim, Eugénie actively rejects this arrangement and her prescribed future. Her most crucial act is leaving Paris to pursue her dream of attending music school in New York City, choosing a life of her own making over a comfortable but imprisoning marriage. In a departure from the source material, and in a change that has drawn critical attention, the anime develops a mutual romantic affection between Eugénie and Albert, and she helps him escape Paris as his own family collapses, with the two ultimately admitting their love for each other.

Throughout the series, Eugénie's key relationships define her struggles. Her relationship with her father is one of cold transactional expectation; she is a pawn in his financial and social games. Her dynamic with Albert evolves from a dutiful and distant engagement to one of genuine emotional connection and partnership in the face of tragedy. The most significant relationship from the novel, her close companionship with her female piano teacher Louise d'Armilly, was adapted out of the story for the anime. Eugénie undergoes notable development from a constrained, melancholic observer to a young woman who takes decisive action to claim her own freedom. Her arc culminates not in a traditional marriage, but in a demonstration of self-reliance and artistic pursuit, highlighting a modern interpretation of independence. Her most notable ability is her musical talent, which represents the only avenue of self-expression and liberation available to her within the repressive grandeur of her social world. In the series' epilogue, which takes place five years after the main events, it is shown that she and Albert have reunited, having rebuilt their lives.