World Trigger, Vol. 1 Ashihara Daisuke (2014)

You may think your neighbors are bad, but at least they are not aliens trying to kill you. 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 adapt other-dimensional technology to fight back, but together with his Neighbor friend Yuma, he will do whatever it takes to defend life on Earth as we know it. Earth remains under constant threat from these creatures, while the elite warriors of Border use alien technology to resist them. When Osamu meets a feisty humanoid Neighbor named Yuma, everything he thinks he knows is turned upside down. Can these two natural enemies ever become friends?