Japan already has probably the strictest immigration controls of any G7 country. Around 3% of Japanese residents are immigrants, the majority of whom are Chinese or Vietnamese working class. The overwhelming majority of visas are for work or study. Spontaneous migration doesn't really exist in Japan. Also, Japan holds the authority to revoke permanent residency for things that wouldn't typically trigger deportation in most countries, even for people without permanent residency. Like failure to pay taxes or having too much medical debt. One scary one is that cops can demand to see a permanent residency card (zairyu card) and if you don't have it on your person, they can arrest you on the spot, fine you 100,000 yen, and then escort you to your residence to verify it exists. Failing to have it on your person enough times is apparently grounds for complete deportation.