Eiko Magami, known to nearly everyone as A-ko, is the protagonist of her story, a sixteen-year-old high school student residing in Graviton City. She is an athletic and attractive girl with thick red hair, typically seen wearing a distinctive sailor-style uniform that originally belonged to her former school. Behind her unassuming teenage appearance lies an awesome and often destructive superhuman power, a heritage hinted to come from her parents, who bear a striking resemblance to two famous American-style superheroes.

A-ko’s personality is a study in contrasts. On most days, she is cheerful, friendly, and polite, expressing a genuine desire to lead an ordinary life despite her extraordinary circumstances. She harbors typical teenage concerns, including a large appetite, a chronic habit of oversleeping, and aspirations for romance and fashionable clothing. She can often be found working a part-time job to fund her shopping trips, hoping to attract a cute boyfriend and experience a perfect summer. However, this pleasant demeanor masks a volcanic temper. When provoked, particularly by her rival, B-ko Daitokuji, A-ko becomes a formidable and dangerous force, prone to large-scale outbursts of violence.

The central axis of A-ko’s world is her lifelong friendship with C-ko Kotobuki, a bond that has existed since their days in kindergarten. A-ko acts as a fiercely loyal and protective guardian to the immature and bubbly C-ko, and this devotion is her primary motivation, driving her to face any threat. This loyalty also puts her into direct conflict with B-ko, a brilliant but spoiled heiress who is obsessed with claiming C-ko as her own friend. Their rivalry is legendary, escalating from schoolyard squabbles into city-block-leveling battles where B-ko deploys an array of advanced mecha and powered armor, which A-ko treats like minor inconveniences.

A-ko’s defining trait is her incredible physical prowess. She possesses immense superhuman strength, blinding speed, and near-invulnerability, making her a classic example of a character who can overpower almost any obstacle through sheer force. To prevent accidental catastrophe, she wears a set of specialized power limiters: black wristbands that regulate her strength, and bon bons on her socks that help keep her abilities in check. Her jet-black Mary Jane shoes also enhance her speed and jumping ability. Even with these limiters, A-ko running late for school leaves a trail of cracked asphalt and miniature earthquakes. If she removes her wristbands, her power becomes truly uncontrollable, allowing a simple flick of her wrist to carve fissures through solid metal or warp gravity, a risk that leads to comedic mishaps when she forgets her own strength.

Throughout the main storyline, A-ko’s role is that of the reluctant but effective hero, battling everything from B-ko’s daily schemes to full-scale alien invasions. Her development often revolves around her struggle to reconcile her superhuman identity with her normal aspirations, such as her attempt to win a boy’s affection in Cinderella Rhapsody, which leads her to neglect and then ultimately reconcile with C-ko. In alternate continuities, such as A-ko the VS, her character is reimagined as a nineteen-year-old bounty hunter on a desert planet, where she shares a grudging and professional partnership with her former enemy B-ko, hunting giant sand turtles while wielding a sword that can harm intangible beings. Through all these incarnations, the core of A-ko remains constant: a well-meaning teenager with god-like power, navigating the absurd chaos of a life where saving the city and getting to school on time are equally pressing concerns.