Natsu, officially spelled Natts, is a prince of the Palmier Kingdom. In his natural form, he resembles a brown squirrel-like fairy with dark brown eyes, a dark orange hair tuft, white neck fur, and a beige underside; he ends sentences with "-natts" in this form. He transforms into a human using the aliases "Mr. Natsu" or "Natsu-san." Journalist Masuko Mika addresses him respectfully as "Natsu-sama" due to her admiration. His human appearance features dirty blonde hair and tanned skin. Initially, he wears a russet brown vest, dark pink long-sleeved shirt, brown buckle belt, dark blue ripped jeans, and brown boots. As an older adult, his hair grows slightly longer and he dons a long dark maroon jacket with brown and gold accents over his signature shirt, light grey jeans, and medium brown boots, retaining the belt.

While guarding the Palmier Kingdom, Natsu attempted to aid a wounded creature, inadvertently allowing Nightmare forces to invade and causing the kingdom's downfall. This trauma instilled intense guilt and lasting distrust. He and Prince Coco escaped to the human world with the Dream Collet. Fleeing Nightmare agent Hadenya, Natsu shielded Coco from an attack, sustaining severe injuries. The Dream Collet absorbed him for protection, scattering its Pinkies and leaving Coco alone. Sealed within the Dream Collet, his release required the combined power of all five Pretty Cure members. After rescue, he distrusted both Coco and the Pretty Cure team but cooperated out of necessity to restore the kingdom. He established Natts House, a jewelry shop serving as the team's base, and provided cases for their Pinky Catches.

Natsu exhibits a serious, sharp-tongued, and stubborn personality, often refusing help and prioritizing blunt honesty over diplomacy, which occasionally hurts others' feelings, though he genuinely regrets causing emotional pain. His journey involves learning trust. Key moments include collapsing from starvation after refusing charity, leading Komachi (Cure Mint) to provide food from her family's sweets shop; he later accepted her advice to use fliers to attract customers. His blunt critique of Komachi's novel demoralized her, but during a Nightmare attack within her story, he encouraged her to defend her work. He afterward offered constructive feedback, mending their relationship and establishing a close bond, making Komachi his primary confidante among the Cures.

In *Yes! Pretty Cure 5 GoGo!*, Natsu and Coco ascend as co-kings of the restored Palmier Kingdom. Natsu receives the kingdom's crown, enabling him to summon the Milky Mirror for Milky Rose. Combined with Coco's power, this facilitates fusion techniques for Cure Dream and Milky Rose. He oversees negotiations with neighboring realms like the Donuts Kingdom and aids Pretty Cure against the art-theft organization Eternal.

The sequel *Kibou no Chikara ~Otona Pretty Cure '23~* depicts Natsu as an adult king actively governing the Palmier Kingdom. He assists Coco with diplomatic issues, such as a failed negotiation with the Donuts Kingdom, and researches the enigmatic Time Flowers appearing in the Cure Rose Garden. Sensing their sinister potential, he visits the human world to warn Komachi, Kurumi (Milky Rose), and Nozomi. During a confrontation with Shadows, he prioritizes protecting their peaceful lives, later acknowledging Kurumi's resolve to transform despite the flowers' dangers. After the crisis, he observes a seed sown by the Time Flowers, expressing faith in humanity's capacity to nurture a positive future.

Natsu's etymology combines with Coco's name to form "coconut," a species within the palm family, reflecting their kingdom's French-derived name "Palmier." The name "Natsu" also means "summer" in Japanese.