Sarah is the firstborn daughter of George Russell, Viscount of Marble, and his late first wife, Lady Frances Russell. She is five years older than her half-sister, Lynn Russell. Having been very young at the time of her mother’s death, Sarah retains no memory of her, and inherits only a flute and a musical score as keepsakes.

Upon first meeting Lynn, Sarah displays a cold and distant demeanor, rooted in unresolved grief and difficulty adjusting to a new family structure. Over time, this coldness softens into a protective and caring relationship. She comes to cherish Lynn as a younger sister, a connection deepened by their shared experience of growing up without a mother.

Artistically gifted, Sarah is a skilled painter and an accomplished flutist. She maintains a long-standing friendship with Arthur Drake Brighton, the eldest son of a noble family, and gradually develops romantic feelings for him.

Her development includes defending Lynn from mistreatment by other members of the household, especially the Waverly family. Sarah evolves from a reserved and lonely individual into a supportive and compassionate sister who actively safeguards Lynn’s well-being.

Later, the Russell family loses their mansion due to unpaid debts, resulting in separation between the sisters. Despite this hardship, Sarah’s foundational bond with Lynn remains central to her character.

In broader narrative contexts, the anime adaptation diverges from the source material. The manga concludes with Sarah marrying Arthur Brighton, while the anime omits this marriage and ends with Lynn achieving a personal victory, leaving Sarah’s ultimate fate less defined in that continuity.