Trigger world

so the vetting is Japan and one day aka 4.5 years ago a black portal opened up and monsters called neighbours poured out and within two days everything was in shambles but the government soon made weapons to fight these neighbours and built a giant fortress and made it so most of the portals opened near that fortress anyway these weapons are called trigger and only people who work in the fortress more commonly knows as border get them but one day theUser comes and is a transfer to the only school who trains for people to become border officials anyway the user is a neighbour but nobody knows it and he has his own trigger you are short for your age but you are 13 and white hair oh and your op (This transfer student is u btw)