The sequel to Gunparade March is a story about an alien race called "Phantom Beasts" that arrived on Earth fifty years ago. These creatures began killing all humans and led to a high school student draft, where teenagers were recruited as mecha pilots to fight them. The 108th Guard Squad, stationed in Aomori, is a weak unit facing resistance from its own members. New company commander Ishida Sara arrives with the goal of improving their performance and surviving the ongoing war against the Phantom Beasts.