This is a show that actually respects your intelligence enough to let side characters matter. Nobody gets strong because the plot demands it; everyone earns their role through strategy, timing, and knowing their limitations. The pacing drags in stretches and some plot threads vanish without explanation, but the core truth holds: this is ensemble action that builds real stakes because no single person can save the day.

A gate to another world opens without warning in Mikado City, and alien creatures known as Neighbors come through it, shrugging off every ordinary Earth weapon. The only force able to stop them is Border, a defense organization whose members fight with special weapons called Triggers. Four years on, the city has rebuilt and its residents have grown used to the ongoing attacks. Osamu Mikumo is a Border trainee, and trainees are barred from using their Triggers outside headquarters. When bullies drag his new classmate, transfer student Yuma Kuga, into a forbidden zone and Neighbors strike, Osamu steps in but cannot win. Yuma activates a Trigger of his own and finishes the aliens quickly, then reveals that he is not with Border at all: he is a humanoid Neighbor from the other side. The result is a sci-fi action series built around alien invaders and the weapons used against them.