Gumimin, also known as Paku-kun, is a male Sweetspet from Sweetsland. Designed as a gummy candy fennec fox, he features light yellow fur, gradient orange-to-yellow gummy ears, and a green-to-lime-yellow gummy tail. His appearance includes reddish-orange eyes, a red heart-shaped nose, a gradient red gummy collar, and a red, yellow, and green beaded bracelet on his right foot.

He arrives in Sweetsland as the "Legendary Sweetspet," launched in a gummy egg projectile by Duke Crème de Brulée's subordinates. The egg crashes into Sweetsland Palace during Princess Mana's birthday preparations, hatching to reveal Gumimin. He immediately consumes his eggshell and devours the princess's birthday cake, displaying an insatiable appetite. Suffering from amnesia that prevents him from recalling his identity or origins, Ruby and others name him "Paku-kun" after the Japanese onomatopoeia "paku paku" for chewing.

His amnesia causes distress, particularly when viewing the power-granting Candy Tower. During a visit, Gumimin consumes a large piece of chocolate dislodged by the Duke's minions, restoring his memory. This reveals his legendary nature but also transforms him into a rampaging monster. In this state, he devours half the Candy Tower and rolls through Sweetsland, destroying buildings indiscriminately. His fury targets the Duke, his initial manipulator, though Princess Mana and the Minister intervene to prevent harm.

Ruby halts Gumimin's rampage by accidentally dropping souvenirs from their time together into his mouth. These spark memories of their bond, calming him and restoring rationality. Acknowledging his destiny, he prepares to leave Sweetsland for a 200-year rest, growing golden angel wings. Ruby, Princess Mana, and other Jewelpets intervene, using combined magic from landmarks and audience energy to perform a "Jewel Sweets Flash." This ritual permanently reverts him to his original form and integrates him into Sweetsland society. He helps rebake Princess Mana's birthday cake and remains with the Sweetspets.