Destroy thy Neighbor! A gate to another dimension has burst open, and invincible monsters called Neighbors invade Earth. Osamu Mikumo may not be the best among the elite warriors who co-opt other-dimensional technology to fight back, but along with his Neighbor friend Yuma, he'll do whatever it takes to defend life on Earth as we know it.

Humanoid Neighbors from another dimension enter the battlefield for the first time! With strange Triggers that defy explanation, they make quick work of even top Border agents until the agents start to fight smart. Can Border turn the tide of battle in time to save Mikado City?