Simone Rolland starts as a fifteen-year-old flower girl in her adoptive parents Paul and Lillian Rolland's rural flower shop on Île de la Cité. While largely detached from political conflicts, she feels a deep connection to fellow commoners. Her adoptive parents provide a kind, doting, and nurturing upbringing, though Simone remains unaware of her adoption.

The arrest of her childhood friend Milan for protesting aristocratic oppression sparks an early turning point, prompting Simone to appeal directly to Duke de Forges for help. Shortly afterward, agents of Madame Catherine under Marie Antoinette's regime murder her parents. This tragedy devastates Simone, fuels her enduring hatred for the aristocracy, and leads her adoptive father to reveal her adoption in his final moments.

Duke de Forges takes Simone in, treating her as a daughter alongside his son Robert. She attends a convent school for elites, where witnessing further injustices against the poor solidifies her resolve to fight back. Adopting the identity "La Seine no Hoshi" (Star of the Seine), she operates as a masked vigilante wearing a red domino mask, a signature red carnation left at scenes, and a blue cap adorned with a white star. Her attire incorporates both red and blue. She wields a basket-hilted cavalry sword—distinct from a lighter rapier—trained by the Duke, accompanied by an owl named Corot and a white stallion gifted by Robert.

As a vigilante, Simone targets corrupt nobles through heists and direct confrontations. She seeks to avenge her parents and protect Parisian commoners from abuses like those inflicted by Captain Jerouls. Her operations sometimes align with another vigilante, "La Tulipe Noire" (the Black Tulip), who provides support.

A profound revelation later emerges: Simone is biologically the daughter of Emperor Franz I and an opera singer, making her the illegitimate half-sister of Marie Antoinette. This forces her to reconcile her hatred for the aristocracy with her royal lineage, complicating her stance toward the revolution. Despite initial shock, she attempts to prevent the execution of the royal family, though ultimately unsuccessful.

Following the revolution, Simone marries Robert de Forges and adopts Marie Antoinette's orphaned children, becoming their stepmother. Her relationship with Milan evolves platonically; though he harbors deeper feelings, he respects her bond with Robert. Her journey concludes with this dual resolution: personal fulfillment through family and an enduring commitment to protecting the vulnerable.