telling a person that has build a successful life after eight years, is assimilated and speaks the language and can support themselves that they have to leave on completely absurd conditions that virtually nobody could meet, including native citizens, is cruel by just about every definition of that term.

Those people have only ever paid in, have much better options than Japan at this point economically given how far the country has fallen behind, and the logical terminus of this is basically being some kind of ethnic chauvinist second world clown country.

If you're even turning skilled tech workers and law abiding people away your immigration problem is solved by virtue of being poor in another 10-20 years. Japan fell below replacement fertility in the 70s, 35% of the population is over 60, good luck caring for those tens of millions of people about to retire.