The story is set in Paris, on the night before the France Revolution. The civilians have been suffering under the tyrannical rule of Louis, the sixteenth. In order to release the people from their suffering, Simone, a young girl whose parents were killed by the aristocrats, decides to challenge the corrupted aristocrats. Covering her face with a red mask and leaving a red carnation as a mark of her presence, Simone is La Seine no Hoshi.