World Trigger

Four years after a gateway to another world opened in Mikado City, attacks by beings called Neighbors have become an unsettling part of ordinary life. Earth's defense rests with Border, an organization whose agents fight using weapons known as Triggers. When transfer student Yuuma Kuga and classmate Osamu Mikumo encounter a Neighbor, Osamu reveals himself as a Border agent but cannot win the fight. Yuuma intervenes with a Trigger of his own and then reveals an even greater surprise: he is a Neighbor from the other side of the gate.