Destroy thy Neighbour! A gate to another dimension has burst open, and invincible monsters called Neighbours 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 Neighbour friend Yuma, he'll do whatever it takes to defend life on Earth as we know it.

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