At first glance, Ibara Naruse and her friends Aoi Fukasaku and Taeko Nomura look like average, carefree high school students. But the streets they walk on, their destination, and their surroundings are anything but normal. As they continue forward, the trio find themselves stepping deeper into an uninhabitable version of Tokyo, one that has been ravaged by a nuclear disaster 20 years ago.

As part of the Dispatch 3rd Special Force Coppelion, known as the Health Care team, Ibara, Aoi, and Taeko are supported by the Japanese Ground Self-Defense Force (JGSDF) and Colonel Onihei Mishima as they scour the eerily silent streets for survivors. Finding the last remaining humans and having them evacuated by the JGSDF's helicopters is a daily occurrence for the girls. But as their work progresses, Ibara and her friends start to question their own humanity—namely, how they themselves are able to survive in Tokyo without any protective gear.

Coppelion was first announced to receive an anime adaptation in 2010, but the project was put on hold after the 2011 tsunami that struck northeastern Japan caused the failure of a nuclear power plant in Fukushima.