At 2:46 PM on March 11, 2011, the Fukushima Daiichi Nuclear Power Plant experiences a black out due to the aftermath of the Tōhoku earthquake and tsunami. The cooling system fails at the nuclear power plant and the temperature of the nuclear reactor rises. The worst case is coming. Scientists face an unexpected situation and government officials are confused by lack of information. Residents says goodbye to their hometown before evacuating.
A strange meteor lands in Japan and unleashes hundreds of insect-like "Legion" creatures bent on colonizing the Earth. When the military fails to control the situation, Gamera shows up to deal with the ever-evolving space adversary. However the battle may result in Gamera losing his bond with both Asagi and humanity.