[throwaway2037]

> a series of one-year guns pointed at your head

Renewals in Japan are guaranteed if you meet the requirements. Japan foreign worker visa rules are very straightforward. The number one cause for concern would be if your business generates insufficient revenue to pay your a minimum salary required by the visa rules. And the minimum is rather middle class. Before you reply very quickly saying: "What if they business has a bad year?" ... please answer from the perspective of other highly advanced, wealthy nations: Do they want to allow people to stay who are running weak/failing businesses? Probably not.

> in Singapore during COVID ... suddenly announcing that spouses of employees could no longer apply for work rights

This is the reason that I never recommend to live in Singapore as a foreigner, unless you are working as a senior manager for a very large corp.

> Countries can and do summarily change the rules for work visas all the time

Not in Japan. In the last 50 years, they have universally become more liberal about allowing highly skilled people to live and work in Japan.