King Donuts reigns over the Doughnut Kingdom, situated east of the Palmier Kingdom. This small blue dragon possesses a dignified yet arrogant personality, consistently ending his sentences with "~dona." As one of the four monarchs guarding keys to the Cure Rose Garden, his abduction by the organization Eternal sparks central narrative events.

Discovered dormant within the Rose Pact artifact, he awakens abruptly and instantly asserts his authority. He openly criticizes Coco and Natts for perceived failures in protecting their allied kingdoms, displaying initial distrust toward their leadership. His haughtiness manifests in correcting perceived slights, rebuking Nozomi Yumehara for close proximity and reprimanding Rin Natsuki for yawning. Despite his pride, he values diligence. Witnessing Rin struggle with exhaustion from overcommitment to sports, family duties, and design work, he counsels her, revealing an unexpected layer of mentorship beneath his stern exterior.

When threatened, he employs a defensive ability, emitting stunning blue light from his hands. After Eternal's agent Scorp attacks to capture him, he retreats into the Rose Pact for safety. He later observes Cure Rouge's new attack, Fire Strike, during the subsequent battle. Following his recovery, he departs for his own kingdom. Maintaining his regal bearing, he offers Syrup pointed advice about properly conveying a sender's emotions during message delivery, emphasizing his insistence on protocol. Before leaving, he provides a calling card, reinforcing his formal approach to alliances.

His role expands the lore of the Four Kingdoms surrounding Palmier, and his key remains essential for accessing the Cure Rose Garden. Though critical of Coco and Natts initially, his cooperation ultimately aids the broader effort against Eternal.