Madoka Kyouno hails from the coastal city of Kamogawa, attending Kamogawa Girls' High School. A pivotal childhood event ten years before the main story saw her nearly drown in the ocean, encountering a mysterious robotic aircraft while her mother perished attempting a rescue. She resides with her uncle, Hiroshi Nakaizumi, assisting first at his restaurant and later his beach cafe. Her cousin Youko, a former Jersey Club member, significantly shaped Madoka's values.

Madoka founded the Jersey Club, serving as its sole member, dedicated to aiding others in tasks from everyday school activities to life-saving interventions. She exhibits an energetic, optimistic personality, intervening proactively without waiting for requests. Upon completing tasks, her signature gesture involves saying "Maru" while drawing a circle in the air, reflecting her perfectionism in helping. She wears a distinctive jersey with the right pants leg and left jacket sleeve rolled up, symbolizing her club commitment. Academically challenged, particularly in math, she excels physically in kendo, wrestling, and swimming due to club activities. Her swimming skills enable multiple rescues, including saving an alien girl named Lan.

Lan recruits Madoka to pilot the green robotic aircraft Vox Aura, which Madoka names "Midori," to protect Kamogawa. Madoka demonstrates natural aptitude despite no prior experience, later wielding Midori's sword and energy shield in combat. Her piloting faces significant challenges: Midori deactivates mid-battle in Season 1, leading to temporary retirement; it reactivates in Season 2 via percussive maintenance. She also temporarily switches bodies with Yurikano during a Polyhedron experiment, gaining insight into others' struggles.

Madoka's relationships drive her development. She befriends Lan (an alien princess from Le Garite) and Muginami (a pilot from De Metrio), integrating them into the Jersey Club. Their friendship endures political conflicts between their home planets, with Madoka mediating disputes. When Lan and Muginami depart Earth at the Season 1 conclusion, Madoka experiences profound loneliness but maintains her resolve. In Season 2, she confronts planetary leaders Dizelmine and Villagulio—delivering gut punches and speeches condemning their warfare—and helps broker peace by altering planetary orbits to prevent collision.

Across all media, including the OVA "Kamogawa Days," Madoka balances Jersey Club duties with assisting her uncle's cafe. Her story concludes with her receiving recognition from global authorities while remaining dedicated to Kamogawa and the Jersey Club's ethos of unconditional assistance.