Japan definitely does allow naturalization for non-Japanese, source: https://en.wikipedia.org/wiki/Japanese_nationality_law
Germany allows too since I have seen many, many first generation immigrants become German citizens.
Germany allows too since I have seen many, many first generation immigrants become German citizens.
"Foreigners over the age of 18 (or age 20 prior to April 1, 2022) may become Japanese citizens by naturalization after residing in the country for at least five years, renouncing any previous nationalities, and proving self-sufficiency through their occupation or existing financial assets."
You have to renounce previous nationalities, whereas the reverse the United States is much more generous towards the possibility of dual citizenship.
I was pointing out that Japan does let people become citizens after they've lived there for a period of time, the OP was suggesting the complete opposite. Renouncing previous nationalities is not the same as Japan not allowing people to become citizens, no matter how long they have lived there.