Charge Mermaid Nanaumi Aoi fights against the evil empire, Great Star Cluster Gozua, but suffers severe injuries in battle. Her life is saved by Shota Moriyama, a young employee at a local machine shop called Moriyama Works. Shota protects Nanaumi while continuing his daily duties at the factory he inherited from his father. With help from longtime employee Genji Shimizu, they turn the workshop into a safe haven for her. By chance, Moriyama Works discovers a mysterious energy capable of multiplying human strength tenfold—Hyper Electron Energy. They begin researching ways to harness it, developing a rechargeable "Hyper Electron Battery." Meanwhile, a shadowy crime syndicate known as Plant, seeking to dominate the city, has been developing technology to transform humans into machines. In their quest for more powerful cyborgs, Plant targets the Hyper Electron Battery and launches an assault on Moriyama Works and the Charge Mermaid team. The ultimate battle between justice and evil over the Hyper Electron Battery begins now!