This is why, unless you plan on running for office, you don’t naturalize in Japan. You’re forced to renounce your first citizenship and after doing so you’re still considered a foreigner for all practical purposes. You become effectively nationless, regardless of your passport or what it says on paper.
Good for these citizens, but there is less than zero public pressure on officials to change these shitty policies/procedures.
“It’s not racism, it’s just that (insert the most racist thing you’ve ever heard in your life).”