Actually, I like the greater worldbuilding, it's Border specifically I take issue with.
So, there's alternate dimensions that draw alien invasions. Cool. They're centralized to this one town in Japan, but they happen all over the world at smaller levels. Okay. So there's an organization that's formed to fight them, right? But they literally don't exist outside of this one Japanese town, despite the fact that they've got all this incredible technology and that these invasions are a global phenomenon. Not only do they not defend anything outside of that town, they literally don't recruit people from anywhere outside of that one prefecture. Not just Japan, mind, but literally that one part of Japan! This is in spite of having huge personnel requirements, and their number one criteria being an attribute that's apparently both in-born and random (trion levels).
And then they take this defense force, consisting mostly of children, and pay them like shit. Like, actual comically poorly paid. Their big incentive for joining a multi-month mission risking life and limb is a 500 dollar bonus. I still can't get over how hilariously poorly compensated even top-rank Border agents are.
It's not totally immersion-breaking or anything, it's just... very dumb, so it's best not to spend too much time thinking about it.
Also, Border is a 100% private group that's apparently empowered to negotiate with legit other planets?