Japan doesn’t mess around when it comes to invaders.
They instantly recognized that the international students con is one of the primary ways takeover invaders get into a country to take over its local companies and drive locals into the streets.
There’s a famous Japanese proverb that says “Let a stranger in and he will drive you from your home“.
Japan clamps down instantly – not after 20 years’ of invasion damage has been done.
https://www.insidehighered.com/quicktakes/2019/06/12/japan-tighten-rules-enrolling-foreign-students