The narrative takes place in Paris on the eve of the French Revolution. Civilians have endured suffering under the tyrannical rule of Louis the Sixteenth. To liberate the people from their plight, Simone, a young girl whose parents were killed by aristocrats, resolves to confront the corrupt nobility. Concealing her face with a red mask and leaving a red carnation as a signature of her presence, Simone becomes La Seine no Hoshi.