Cocolu, Princess of the Spirit World, is one of five contenders for the Platinum Princess title. Though seventeen, a mysterious curse traps her appearance at age ten, a fate shared by all candidates. Shy, gentle, and perpetually self-doubting, she speaks softly and politely. She frequently laments her lack of presence compared to rivals like Yucie and Glenda, often sighing, "I guess I don't have much presence." Yet beneath her quiet exterior lies deep kindness and encouragement for friends, revealing resilient strength over time. Initially, she seeks genuine companionship over the Eternal Tiara.

As a Spirit World native, she phases through walls, evades physical harm as attacks pass through her intangible form, and counters assaults. Her steward, Chawoo, a ghost from a non-human spirit race, hides in her shadow, shapeshifts to impersonate her, and supports her despite her disapproval of his boastfulness.

Relationships fuel her growth. Yucie becomes her first close friend after defending her from bullies, forging a bond untouched by rivalry. Her connection with Beth shifts from tentative understanding to a heavily implied romance. She maintains neutral or lightly friendly ties with Glenda and Elmina, often mediating their conflicts.

Cocolu matures from timidity to confidence, bolstered by Yucie and her friendships. In the climax, she and the other candidates renounce their claims to support Yucie’s wish to save Prince Arrow. This sacrifice triggers their disappearance, as unchosen candidates vanish. After Yucie resolves the Magic World’s lost princess tragedy, Cocolu and the others return. With the curse lifted and the tiara sealed, she resumes life at the Princess Academy, finally able to grow physically and cherish her friendships.