Raeliana McMillan is the central character of the anime Why Raeliana Ended Up at the Duke's Mansion. She is the reincarnation of Rinko Hanasaki, a young woman originally from the modern world whose life began in twenty-first century Seoul. Rinko was forced to take a gap year between high school and university after being waitlisted by all of the schools she applied to. Her family background had a clear influence on her character: her mother was strict and demanding, described as tough like a military general and always pushing her toward success, while her older brother, three years her senior, was someone she did not get along with. Her ordinary life ended abruptly when she was pushed to her death from a building by a mysterious figure. She then awoke in an unfamiliar place, inside the body of Raeliana McMillan, an eighteen-year-old noblewoman and the eldest daughter of a wealthy baron, in a fantasy world she recognized as the setting of a novel she had once read.

In the story she knew, Raeliana was a minor supporting character with a tragic fate. Her fiancé, Francis Brooks, was slowly poisoning her to death so that he could take over the McMillan family's company while the family was lost in grief. Because the reincarnated Raeliana remembered the original plot, she understood immediately that her new life was in grave danger. Her chief motivation is therefore survival. Determined not to die a second time, she takes decisive action and approaches Duke Noah Volstaire Wynknight, the most powerful noble in the kingdom, and proposes a contract arrangement. She offers to keep silent about his secret possession of the royal seal, and in exchange he agrees to act as her fake fiancé and protector for a set period. This deal shields her from Brooks and pulls her into the political intrigues of high society.

Raeliana's personality is open, outgoing, and direct. She is not shy and tends to say exactly what she thinks without holding anything back, which often comes across as sarcastic and dramatic. She has little tolerance for being looked down on and rarely lets fear control her, facing threats with unusual nerve. In difficult situations she keeps a cool head and searches for practical solutions instead of panicking, and she is quick-witted enough to talk her way out of trouble. Toward the people she loves, she is warm and protective, especially with her younger sister Rosemary, for whom she shows particular softness. The only person who consistently manages to fluster her is her contract fiancé, Noah.

Her role in the story is that of the protagonist whose choices drive the plot forward. Rather than passively accepting her destiny, she uses her knowledge of the novel to outmaneuver those who wish her harm, turning a doomed side character into an active player in the kingdom's political games. She repeatedly handles schemes, social rivals, and even a kidnapping attempt, relying on her wits rather than any special power. The most important relationship in her life is with Noah. What begins as a cold, businesslike arrangement gradually develops into genuine affection, though Raeliana is slow to trust his feelings because she believes he is meant to end up with the story's original heroine, Beatrice Tranchett. Over time the two learn to rely on each other, and the fake engagement becomes a real one. Her other key relationships include Francis Brooks, the former fiancé whose murder plot she works to escape; Rosemary, her beloved little sister; Adam Taylor, Noah's loyal knight who becomes a trusted ally; and Vivian, a noblewoman who acts as an antagonist toward her.

Raeliana undergoes clear development across the story. She begins terrified by her situation and focused only on survival, but as she settles into life at the Wynknight mansion and navigates noble society, she grows more confident and secure in herself. The contract relationship forces her to adapt, and in the process she uncovers new strengths, learns to trust others, and finds her own path rather than simply following the novel's script. Her journey ends in happiness: she marries Noah and becomes pregnant with their first child, a daughter named Aria. Noah eventually learns of her reincarnation and accepts it, promising to find her again in the next life.

In terms of abilities, Raeliana has no magic or combat skills. Her strengths are her memory of the original novel's events, which gives her a kind of foresight, her modern-world knowledge and perspective, sharp observation, persuasive speech, and logical problem-solving. She excels at negotiation and social maneuvering, and her composure under pressure allows her to survive situations that would overwhelm someone less resourceful. Her blend of intelligence, courage, and emotional warmth is what allows her to change her fate and build a lasting bond with Noah.