In the anime Why Raeliana Ended Up at the Duke's Mansion, the central character is Raeliana McMillan, who is also referred to by the variant name Katy McMillan in some sources. Her story begins not in the world of the story, but in modern-day Korea, where she lived as a young woman named Eunha Park. After being pushed from a rooftop to her death, Eunha awakens in the body of Raeliana McMillan, a character from a novel she had read.

This new identity comes with a severe and immediate problem. Raeliana is a minor character whose death serves as the catalyst for the main plot of the original novel. Her fiancé, Francis Brooks, is destined to poison her to seize her family's fortune, an event she knows is fast approaching. This knowledge defines her core personality: she is resourceful, pragmatic, and fiercely determined to survive. Unlike a passive heroine waiting to be rescued, Raeliana is proactive. She uses her foreknowledge of the novel's events as a tool, strategically planning to change her own fate.

Her primary motivation is simple yet powerful: to avoid being murdered a second time. To accomplish this, she devises a risky plan. Instead of trying to expose her murderous fiancé, she goes directly to Duke Noah Wynknight, the novel's powerful and dangerous male protagonist. She proposes a fake engagement, offering to keep his secrets in exchange for his protection. This act demonstrates her boldness, her ability to negotiate under pressure, and her willingness to align herself with a man she knows to be cunning and potentially just as lethal as the threat she is fleeing.

Throughout the story, Raeliana takes on the role of a woman trying to navigate high society while subtly altering the course of the narrative. As she moves into the Duke's mansion to legitimize their fake engagement, she undergoes bridal training in etiquette, dancing, and other social graces. However, she is not content to be a passive participant. When she discovers that the original heroine, Beatrice, is missing, she realizes her actions have changed the story in unpredictable ways. This creates a new layer to her role, as she must contend with the consequences of her own success in surviving.

Her key relationships are complex and evolve significantly. With Duke Noah Wynknight, her relationship begins as a cold, calculated contract, but the boundaries slowly blur as they grow closer, developing genuine affection despite her initial understanding that he is fated to fall for someone else. Her relationship with her former fiancé, Francis Brooks, shifts from one of naive acceptance to wary avoidance as she actively works to escape his murderous plot. She also forms a bond of trust with Adam Taylor, the Duke's stoic and loyal knight who is assigned to guard her, and she shows him a kindness that surprises him.

As the story progresses, Raeliana undergoes significant development. She starts as a panicked woman scrambling for a way out of a predetermined death. By taking control of her situation, she grows more confident in her ability to act, no longer merely reacting to the novel's plot but actively forging her own path. She moves from simply surviving to trying to unravel the mysteries behind her reincarnation and her new world. Her journey is one of shifting from a supporting character in someone else's story to the protagonist of her own life.

In terms of abilities, Raeliana possesses more than just knowledge of the future. She is an excellent marksman, a skill she learned from her new family's father, who is an avid huntsman. This talent proves to be a notable ability, allowing her to defend herself and others in dangerous situations. This combination of strategic foresight and practical skill makes her a uniquely capable figure in her new world.