Tsubomi Moroboshi is one of three high school students killed when the city's protector, UFO-man, accidentally crushed them during a monster attack. Resurrected with supernatural abilities, she becomes a giant heroine defending the city alongside her friends Silk Koharuno and Vivienne Ōtori.

An enthusiastic cosplayer, Tsubomi embraces her new role without shame or embarrassment, unlike her uncomfortable teammates. This attitude directly hinders her combat effectiveness because their battle suits' power source relies on feelings of humiliation generated as the suits deteriorate. Her inability to feel this humiliation makes her the weakest of the trio in raw power.

Consequently, she favors clever tactics and trickery over direct confrontation. Her cosplay hobby provides practical cover for her superhero identity; she openly wears miniature versions of her battle suit, passing them off as ordinary costuming, thus avoiding typical secret identity issues.

In her normal form, she wears glasses and styles her black hair in pigtails; her glasses disappear during transformation. Public observers and media refer to her as "Loli" due to her comparatively underdeveloped chest. She maintains close bonds with Silk and Vivienne, demonstrating awareness of interpersonal dynamics like Vivienne's unspoken feelings for Silk. Her exhibitionist tendencies persist in her superhero activities, viewing battle nudity as an extension of her cosplay passion.

Her characterization remains consistent throughout the core series, with no significant development or alterations noted in supplementary media.