"Coppelion" is set in a post-apocalyptic Tokyo, 20 years after a catastrophic nuclear meltdown has rendered the city uninhabitable due to high radiation levels. The story centers on a group of genetically engineered high school girls known as the Coppelion, who are dispatched into the desolate ruins of Tokyo by the Japan Ground Self-Defense Force. These girls possess enhanced abilities, including immunity to radiation, making them uniquely suited for rescue and reconnaissance missions in the contaminated zone.

The main trio consists of Ibara Naruse, the determined and strong-willed leader; Aoi Fukasaku, the cheerful and empathetic medic; and Taeko Nomura, the quiet and observant scout. Their mission is to locate and assist any survivors still living in the abandoned city. As they navigate the eerie, decaying landscape, they encounter a variety of challenges, including hostile wildlife, environmental hazards, and remnants of the old world that hint at the city’s tragic past.

Throughout their journey, the Coppelion uncover the truth behind the nuclear disaster and the ethical dilemmas surrounding their own creation. They face moral questions about their purpose and humanity, as well as the consequences of human interference with nature and genetic engineering. The narrative explores themes of survival, sacrifice, and the resilience of the human spirit, while also delving into the darker aspects of scientific experimentation and societal collapse.

The series balances action, mystery, and emotional depth as the girls confront both external threats and internal conflicts. Their interactions with survivors, military personnel, and other Coppelion units reveal layers of complexity in the post-disaster world, highlighting the struggles of those who remain in the wasteland and the lingering hope for a brighter future.