A young boy in a peaceful seaside town gets more than he bargained for when he takes home a mysterious egg. When it hatches, out comes a baby turtle that grows into a new version of Gamera. But will it become powerful enough in time to defeat the rampaging monster Zedus?

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.