Nineteen years ago, the world was devastated when the planet was attacked by an immense enemy force. A climactic battle brought an end to the war and should have saved Earth once and for all. But in present day Japan, Hayato Jin watches a battle unfold from the command center of Saotome Research Lab at the base of Mt. Asama. It turns out that a war with a new enemy has been ongoing in secret. However, nobody knows what awaits at the end of the fight – survival or annihilation.