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.

Border headquarters wants Yuma's powerful Black Trigger - and they want it desperately enough to send their top three squads to steal it. The Tamakoma branch is one step ahead, having already safeguarded Yuma, Osamu and Chika by recruiting them to their group of eccentric and talented agents. And Jin's precognition powers put him two steps ahead: he ambushes the thieves en route!