Duke Crème de Brûlée is a human who holds the title of Duke in the Sweetsland Kingdom. His primary motivation is a desire to rule the kingdom himself. To achieve this goal, he proposes marriage to Princess Mana, the rightful heir to the throne. Following her rejection, he sets in motion a plan to seize power by force.

His scheme involves launching a gummy egg containing a male Sweetspet named Gumimin toward the Sweetsland Palace. This action was intended to trigger Gumimin's transformation into a legendary monster to destroy the royal family's legacy and clear a path for the Duke to take the throne. The plan is complicated when Gumimin suffers from amnesia upon arrival, leading the Jewelpets to call him "Paku."

The Duke is assisted by a spy, a Sweetspet named Chocolat, who is tasked with observing the Jewelpets. He is also served by macaron Sweetspet assistants, whom he instructs to address him as "sire." Other characters in the film frequently mispronounce his name.

His plot ultimately fails. Gumimin eats the chocolate from the Candy Tower, a critical structure that provides power to the Sweetspets, but is saved by the combined efforts of the Minister and Princess Mana. Following this failure and Gumimin's restoration, the Duke undergoes a change of heart. He abandons his antagonistic goals and decides to assist in rebuilding the Candy Tower, allowing Gumimin to remain in Sweetsland.

He has green eyes and pink hair that reaches his shoulders. He is typically seen wearing three-quarter-length pants and has a ponytail hairstyle accompanied by an ahoge.