As far as I'm aware Japanese immigration policy for skilled workers is relatively lenient, it's just not generally considered an attractive place to migrate to from places that generate a lot of migrants.
It's lenient for certain sectors--programming, engineering. Niche STEM stuff where English is expected as the uniting language. But for anything else, it can be very difficult to move there.
But that leniency only comes into effect when you prove without question that it's near impossible to source local talent to fill a job, and the Japanese are extremely educated, so you're usually going to find companies will hire domestically before gambling on someone from the west who's used to superior salaries in USD.
Even if you're the world's best, your salary will drop to about 1/2 or 1/3 of what you can make in the US.
