It was always ridiculously easy to get Japanese citizenship. 5 years of residency, don’t break any laws including traffic, pay your bills on time. Done.

It has recently been changed so that you now require 10 years of residency.

https://www.turning-japanese.info/p/misinfo.html

So is it 5 or 10 years? Another person responding in this same branch says it used to be 10 but is now 5.