Lynn, born Rin Midorikawa, is the Anglo-Japanese daughter of English nobleman George Russell and his Japanese wife, Misuzu Midorikawa. Her early years in Japan concluded abruptly at age five when a car accident during their journey to England claimed her mother's life. Her father gently softened this trauma, explaining Misuzu's absence as having gone to "a far away place" due to "God's will," a loss Lynn did not initially grasp fully yet sparked her resilience.

Relocating to her father's Marble Mansion estate in England, Lynn faced isolation exacerbated by George's frequent work absences and the harsh realities of aristocratic society. She endured hostility from her step-siblings Thomas and Mary Waverly, who bullied her, and their mother, Baroness Madeleine, who openly disapproved. Her paternal grandfather, the Duke of Warbawn, rejected her mixed heritage, dismissing her as the child of "an unknown Eastern woman." Amidst this adversity, Lynn drew strength from a promise made to her late mother to become a "strong and elegant lady," a vow symbolized by a keepsake called the Lady's Key and forming her core motivation.

Her relationship with older half-sister Sarah transformed from initial coldness—marked by Sarah once rejecting Lynn's bouquet—into profound mutual devotion. Sarah emerged as a protective figure, defending Lynn against the Waverlys. Beyond family, Lynn formed significant bonds: with the unconditionally supportive Edward Brighton and Arthur Brighton, who mentored her in horseback riding. Her affinity for animals manifested in caring for her kitten Queen, adopting Mary's abandoned cat Prince, and raising their kittens. She developed exceptional equestrian skills, notably with Arthur's horse Alessandra, who responded solely to her and Arthur.

Maturing, Lynn enrolled in an elite school to pursue the prestigious Lady's Crest award. There, she confronted renewed antagonism as Mary Waverly allied with rival Vivian to sabotage her efforts. Lynn's perseverance culminated in triumph at a climactic Olympic qualifying horse race. This victory secured her the Lady's Crest, prompted her grandfather's acceptance, and affirmed her commitment to courage and kindness. In a subsequent reflective moment, she directly addressed the audience, reaffirming her lifelong dedication to becoming a true lady.

Her portrayal differs between the manga and anime. The manga concludes with Lynn marrying Edward after financial ruin forces the Russells from Marble Mansion, resulting in twins and a stable future. The anime adaptation omits George's death and remarriage, keeps Lynn in England throughout, and reconfigures characters like Mary into a primary antagonist. It also softens elements from the source material, reducing the Duke's racism and eliminating scenes of physical abuse, while adding original themes addressing child welfare and class divides.

Lynn's Japanese heritage, reflected in her original name Rin Midorikawa, remained integral to her identity, serving as a cultural touchstone and narrative device exploring belonging. Creator Yōko Hanabusa intentionally designed her as half-Japanese to help Japanese audiences relate to her struggles within English high society. Across all media, Lynn's journey consistently centered on navigating grief, prejudice, and social hurdles through unwavering resolve and compassion.