Synopsis
When a portal to another world suddenly opens on Earth, Mikado City becomes the target of an invasion by mysterious beings called "Neighbors," which are immune to conventional weapons. The Border Defense Agency is formed to fight this threat using specialized weapons known as "Triggers." Even after the portal first appeared, Neighbors continue to endanger humanity, keeping Border agents on constant alert. In this dangerous situation, trainees like Osamu Mikumo are forbidden from using their Triggers outside the base. This rule is challenged when a new transfer student in his class is tricked into entering a restricted area by bullies and then attacked by Neighbors. Driven by his beliefs, Osamu steps in, only to see the transfer student, Yuuma Kuga, easily defeat the invaders, revealing Yuuma's true nature as a disguised humanoid Neighbor.
