Seventeen-year-old Madoka Kyouno is a spirited girl who runs the Jersey Club at her high school in the coastal city of Kamogawa, a club with a simple philosophy: to help anyone in need. Her life takes a dramatic turn when she meets a mysterious, silver-haired girl named Lan, who reveals herself to be an alien princess from the planet Le Garite. Lan has come to Earth to recruit Madoka as the pilot of a powerful, ancient robotic weapon known as a Vox, specifically the green unit Vox Aura. Madoka discovers she has a unique, forgotten connection to this mecha from a childhood incident, and driven by her desire to protect her hometown, she agrees to pilot it.

Soon after, a bubbly and seemingly carefree transfer student named Muginami arrives at Madoka's school. She is also an alien, but from De Metrio, a rival faction to Le Garite. Initially acting as an adversary to claim the Vox units for herself, Muginami quickly becomes the third member of the Jersey Club and the pilot of the third Vox, the orange Vox Ignis. The three girls form an unlikely but close friendship as they use their mecha, collectively known as the Ovids, to defend Earth from various threats.

The central conflict stems from a generations-long intergalactic war between Le Garite and De Metrio. Le Garite has an alliance with a powerful Earth-based organization called Novumundus, which operates from a mobile offshore base named Pharos. The primary antagonists are a group of charming but dangerous pirates from De Metrio, who are initially led by the charismatic Villagulio. However, as the story unfolds, it becomes clear that neither side is entirely right or wrong. The war is driven by a prophecy and a deeper mystery: the Vox units are linked to a dangerous phenomenon called the Rin-ne, a dimensional rift that could lead to the destruction of worlds. Madoka’s natural and uninhibited piloting style inadvertently triggers this power, making her a key to resolving the ancient conflict.

The narrative is split into two seasons. The first season focuses on the trio learning to work together, protecting Kamogawa from attacks, and uncovering the true intentions of Villagulio and his crew. The second season deepens the lore, introducing Lan’s older brother, Dizelmine, the king of Le Garite, and revealing the tragic past of Villagulio’s sister, Yurikano, whose consciousness is trapped within the Rin-ne. The plot escalates from a simple defense of Earth to a mission to prevent a cosmic catastrophe. The girls ultimately discover that the Vox units are not merely weapons, but tools meant to alter the orbits of the two warring planets to prevent their collision, a solution lost to history. The series concludes with the resolution of the war, as Madoka’s unwavering determination helps heal the rift between the two worlds and frees Yurikano, allowing Lan and Muginami to return to their respective homes after forging an unbreakable bond with Earth and each other.