You thought your neighbors were bad...but at least they're not aliens trying to kill you!

Earth is under constant threat from Neighbors, invincible monsters from another dimension that destroy our way of life. At least we have the elite warriors of Border, who co-opt alien technology to fight back! Meet agent Osamu Mikumo, not the best, 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?