Rupert de Gilet (ルパート•ド•ジレ, Rupāto do Jire) is the reigning king of Sauville at the year 1899. He personally witnesses the powers of the alchemist Leviathan and, despite his fears about his supernatural powers, led the kingdom with the alchemist's guidance.
He was charmed by Coco Rose's beauty, and he married the French lady on the year 1897. However, when she becomes completely absorbed in the occult, his relationship with her started to deteriorate.
The King later attempted to kill Coco Rose upon his discovery on the queen's mulatto son and kills her maid (who posed as the queen) on 1900. He would then be offered help by the Science Academy's Jupiter Roget to keep the events of the incident a secret, which involves getting the professional performer Nicole Leroux to pose as the queen before killing her himself in order to keep the replacement from being exposed.
He would later order the repatriation of non-Sauvillean citizens to their respective countries after signs of civil unrest began to break out in Saubrème.