World Trigger Vol. 15

When a gate to another world suddenly opens one day in Mikado City, monsters called "Neighbors" pour through and begin attacking the city. In response to the alien invaders, an organization called the Border Defense Agency is established, which possesses the means to fight back against the Neighbors using special weapons called “Triggers.” Four years later, Osamu Mikumo is a Border trainee whose life suddenly changes when he befriends a strange white-haired transfer student named Yuma Kuga, whom he discovers is actually a humanoid Neighbor. Completely oblivious to life in the city, it’s up to Osamu to help him survive. But will he be able to keep him hidden from Border?
Notice: This manga is written in Japanese.