Synopsis
A gate to another world suddenly opens on Earth, leading to the invasion of Mikado City by mysterious beings known as "Neighbors"—creatures that are immune to conventional weapons. In response, the Border Defense Agency is formed, using special weapons called "Triggers" to fight the Neighbor threat. Years after the gate first appeared, Neighbors continue to pose a danger, and Border members remain on constant alert to protect the planet. In this tense environment, trainee members like Osamu Mikumo are forbidden from using their Triggers outside headquarters. However, when a new transfer student in his class is dragged into a restricted area by bullies and attacked by Neighbors, Osamu feels compelled to act on his principles. To his astonishment, the transfer student, Yuuma Kuga, swiftly defeats the aliens, revealing himself to be a humanoid Neighbor in disguise.
