They Thought He Was A Powerful S-Rank Trigger But He Actually Was E-Rank

Mikado City is attacked by bizarre creatures known as "Neighbors," evil monsters impervious to ordinary weaponry, after a portal to another realm suddenly emerges on Earth. In reaction to their arrival, the Border Defense Agency was formed to confront the Neighbor threat using special weaponry known as "Triggers." Even after several years have passed since the gate initially opened, Neighbors remain a menace, and Border members remain vigilant to safeguard the planet's safety.

Anime:World Trigger