Mireille (Mileille in English) is an NPC found in the Sky World on the tenth floor of the Tower.
She is the daughter of Charles and the twin sister of Jeanne.
Born to Charles, leader and founder of the Resistance movement against Byakko. After her father's death from Byakko's forces, Mireille began to obsess over power as she felt it was the only real way to survive in the world. For this reason she joined forces with Byakko and became part of his scheme to obtain the White Sphere.
Pretending to be captured, the heroes rescue her from Byako's Floating Fortress. Telling her they plan on reuniting her with her sister, she asks them frantically where she is. Once the party reveals Jeanne's location, Baykko appears and Mireille reveals her true allegiance.
She then travels with Byakko to capture her sister and go to the Sacred Palace to retrieve the White Sphere.
At the palace, Byakko obtains the Sphere and then reveals his plans to dispose of the sisters now that they are no longer needed. Sending a wave of destructive energy to kill Mireille first, but her sister Jeanne jumps in the way to shield her and is killed instead. After the heroes slay Baykko, Mireille is found grief striken and sobbing over her dying sister. Their tears meet and create the true White Sphere, something only Jeanne had known would happen. With her dying breath, Jeanne gives the sphere to the heroes. Mireille begs them to continue their journey and remains in the Sacred Palace.