Kamogawa is a seaside city in the Chiba prefecture. There lives Kyouno Madoka, a student at Kamogawa Girls' High School, and the only member of the Jersey Club. Madoka prides herself on being bright and energetic, and spends much of her time helping people.
However, her life changes one day when the mysterious girl Lan asks her to "pilot a robot". In order to protect the citizens of Kamogawa, Madoka agrees and engages in battle against extraterrestrial invaders.
Madoka and Lan are later joined by Muginami, and the trio works together to protect the Kamogawa seas, piloting robots called Vox.