Should I keep the Japanese citizenship or become an American citizen? You can keep both. However, there are implications involved should you decide to pursue US citizenship. First about Japan: The Japanese government turns a blind eye regarding dual citizenship. Unless you formally declare that you choose US citizenship over your Japanese citizenship, there is little if anything the Japanese government can do. The Japanese government does not ask any questions at the airport about stamps in your passport. In fact, now in Japan the passport checking is increasingly done automatically （自動ゲート, 顔認証ゲート）。Many Japanese have dual citizenship and they have no problems flying between the two countries. Lastly, the Japanese government doesn’t just “press a button” when you naturalize as a citizen in another country, rendering your Japanese nationality null and void. This is all nonsense that is perpetuated again and again by those who know little if anything about the process. (Mo...