Kuroda Masago is a teenage student in the Plum Section of Sunshine Academy, one of the few human males in the class. He has a slender build, slightly tanned skin, short and spiky light brown hair, and brown eyes. His personality is outgoing and playful; he is known as the class clown and enjoys pulling pranks and making others laugh. However, his spirited nature sometimes leads him to be thoughtless or inconsiderate, especially when his enthusiasm overrides his awareness of others' feelings. This contrasts with the more reserved demeanor of his best friend and roommate, Mikage Shiraishi, with whom he shares a close bond. Later, he also rooms with Jasper and becomes attuned to his friend's emotions.

Masago's primary motivation revolves around his admiration for the Jewelpet Garnet, on whom he develops a crush early in the series. He goes to great lengths to impress her, at one point attempting to direct a film starring her to support her dreams. When his impulsive actions inadvertently cause problems for the production, he recognizes his mistake, feels genuine remorse, and works through the night to rewrite the screenplay, demonstrating a capacity for growth and dedication. Garnet, focused on her own aspirations, gently turns down his romantic feelings, but they remain on good terms.

In the broader story, Masago serves as a lighthearted presence among his classmates, often providing comic relief even as misfortune tends to befall him. During the final conflict, when Dark Jewelina freezes many students in ice, he is among those affected. His character arc culminates in the series epilogue, where he has become a movie director and continues to collaborate with Garnet professionally. While he does not possess magical powers, his notable abilities lie in his creativity, humor, and eventually his filmmaking and storytelling talents. His relationships, particularly with Mikage and Garnet, shape his development from a carefree prankster into someone capable of earnest effort and long-term dedication to his craft.