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. Should Border, Earth's defense agency, admit a Neighbor into their ranks? Jin and Arashiyama Squad think so, and they clash against headquarters' top agents to preserve Yuma's right to enlist. After the brutal fight against his friends and peers, Jin makes an unimaginable sacrifice to put an end to the hostility and protect Yuma's future at Border.