Demande is Prince of the Black Moon and one who willingly serves under and secretly follows the orders of his one true master, Wiseman. He is romantically charmed and attracted to Neo-Queen Serenity, Sailor Moon's future self, and is determined to have her all to himself by any means necessary.
His is the most loyal servant and devoted minion of Wiseman/Death Phantom, whom he considers his one true master and confidant/friend and is, therefore, glad to work for him. He promises to obtain the immeasurably powerful Silver Crystal from "the Rabbit" and destroy it.
However, he eventually came to realize that Wiseman was, in fact, taking advantage of him and demanded to see his true form before he was put under Wiseman's mind-control and given an even stronger earring made of the Malefic Black Crystal. He was ordered to capture Sailor Moon again and force her to use the Silver Crystal of the past. Once breaking free, Demande sadly admitted that he was being toyed with all along, and was forced to kill Saphir. No longer trusting anyone, he managed to take both Silver Crystals of the past and future with the intention touching them together, thus destroying everything. But he was stopped by Sailor Pluto, who have stop time and told Sailor Moon to take both back.
To make amends for ever trusting Wiseman, he defended Sailor Moon from Death Phantom. Unfortunately, Wiseman's power was too much for him and he was vaporized, but before it happened he looked up at Sailor Moon and called her "Queen".