Black Bullet, Vol. 4 (light novel): Vengeance Is Mine

One of the giant Monoliths that protects Tokyo Area from the virally superpowered Gastrea creatures has been destroyed. And right on schedule, the Stage Four 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 Rentaro and his friends? The near-future thriller of post-apocalyptic survival continues!