[throwthrow564]

That's just false. Becoming a Japanese citizen isn't harder than being a permanent resident and in some cases it's easier (https://www.turning-japanese.info/2010/07/faq-which-is-more-...). The most common thing is that people don't want to become Japanese citizens because it requires giving up their native citizenship and the benefits of permanent residency is basically equivalent to that of citizenship (other than voting).