One of the giant monoliths that protects Tokyo Area from the virally-superpowered Gastrea creatures has been destroyed. And right on schedule, the Stage 4 Gastrea Aldebaran leads an invading army of the monsters into the city. The elite self-defense forces are sent to face them, and the terrible sounds of war echo across a newly-christened battlefield - but soon a tense silence falls. What is it that appears before the eyes of Rentarou and his friends? The near-future thriller of post-apocalyptic survival continues!