An orphan adopted by a wealthy elderly woman following her mother's death, Karen originates from Hans Christian Andersen's "The Red Shoes" as adapted in the anime *Andersen Monogatari*. Initially humble, she develops a consuming obsession with vanity, fixating on a pair of red shoes she acquires despite knowing they are inappropriate for mourning or religious occasions.

Her background of poverty and loss, compounded by a lack of maternal guidance, sets the stage for her downfall. After adoption, she disregards warnings about the shoes' impropriety and wears them to church, unleashing a supernatural curse. This curse forces her into uncontrollable, ceaseless dancing. Unable to stop or remove the shoes, she dances day and night through fields and forests, enduring physical exhaustion and terror.

Her development focuses on seeking redemption. Realizing the consequences of her vanity, she begs an executioner to amputate her feet to break the curse. The severed feet, still encased in the red shoes, continue dancing independently. Afterward, crippled, Karen dedicates herself to piety and charity. She serves in a parsonage, reflecting on her past and finding peace through humility and religious devotion, achieving spiritual redemption that contrasts her initial downfall.

In the anime adaptation, Karen's narrative remains faithful to the original tale's themes of punishment for vanity and the path to atonement, retaining the core storyline and personality across episodes.