In a landmark ruling yesterday (see articles below) first testing the waters for allowing Japanese to have more diverse roots in a legal sense, the Tokyo District Court has just ruled that Japanese who obtain other citizenships do not have constitutional protections from being subsequently deprived of Japanese citizenship. This means:
a) If you as a Japanese citizen naturalize in another country, then when the Japanese government decides to take away your Japanese citizenship, you have no legal recourse under the Japanese Constitution. It can be unilaterally revoked at the government’s discretion.
b) If you as a native-born Japanese citizen have dual nationality due to having international parents, and if you do not declare to the Japanese government that you are a Japanese citizen only (and have renounced all other citizenships by age 22 — as Osaka Naomi, referred to below, reportedly did), then the Japanese government can revoke your Japanese citizenship and not deprive you of any Constitutionally-guaranteed rights.
Conclusion: Essentially, nothing has changed in practice. The lower judiciary has essentially just made its stance against dual nationality clear. Take into account that this ruling, handed down by a notoriously conservative branch of Japan’s judiciary (yes, Tokyo District and High Courts are actually well-known around the Japanese legal community for their very conservative judgments), has merely affirmed what was already true: “two passports = untrustworthy”. And their legal reasoning mentioned in the articles below reflects that logic, based upon paranoid pre-war arguments about individual mixed allegiances threatening the motherland, etc., with no need to update for the complexities of the modern world. Should the plaintiffs decide to appeal this case, then the Tokyo High Court and probably eventually the Supreme Court will affirm the lower court’s ruling. So it’s definitive.
What to do about it: Continue to follow Debito.org’s advice: If you have two passports, you always claim to be solely Japanese by age 22 but secretly keep renewing your foreign passport. The Japanese government is still not fully enforcing any draconian “show us a revoked foreign passport by age 22 or we will revoke your Japanese citizenship” towards all its citizens with international roots. Given Japan’s dropping population, that’s probably not in its interest. But if the Japanese government ever gets around to doing that, based upon yesterday’s ruling, as far as the Japanese judiciary is concerned it will have free rein.