All right, you remember Yozakura Quartet, right?
The premise there was that magic worked, demons were real. Thus normal, non-magical people wanted all the demon people to live in a ghetto-city set aside for demons. That premise was a very believable approach to urban fantasy. Japanese people can be pretty xenophobic, and one could easily imagine the Japanese government going along with a plan to make demons into the next version of Okinawans – i.e. lower-class people with no money and no political power.
Premise: A dimensional gate opens in Mikado City and extra-dimensional sci-fi aliens called “NEIGHBORS” invade through it.
The Japanese army has little success in stopping them.
A mysterious organization, BORDER, appears, fights the aliens effectively, and even though the gate stays open, most of the population decides to stay in Mikado City. Incidentally they build a huge fortress overnight, and no one bothers them about land use rights.
And … the Japanese government … is supposed to be silent while all this happens. There’s an extra-dimensional menace, the army is powerless, and the only defenders of Japan are mysterious strangers. And the Japanese government just sits back and ignores this.
The sci-fi trappings don’t change the essence of the story. The two main characters are a fish-out-of-water boke and a tsukkomi, designed to appeal to young teenagers. They are both straight males, so their friendship/bromance is going to be G-rated.
Now, you might reasonably object that Beyond the Border had a premise that was almost as weak, and served a nearly-identical purpose of giving a meaningful backdrop to the angsty teenage romance that formed the meat of the story. Yes, but that story had romance, plus a sexy cosplaying demon-mom showing up for comic relief and fan service.
I don’t see nearly enough fan service in World Trigger to keep me watching a sci-fi-monsters-invade-the-school show. By contrast, the second episode of Karen Senki has very believable human behavior and human stupidity. The tech approaches sheer Hollywood action-extravaganza levels of silliness, but I can forgive that if the visuals are good.