2025-08-06

Naturalization is the process by which a foreign national residing in Japan acquires Japanese citizenship. After naturalization, you will live as a Japanese national and use your “Japanese name”. In this issue, we will explain the rules of “Japanese name” after naturalization.

What is naturalization?

Naturalization is the process by which a foreign national residing in Japan acquires Japanese nationality. Specifically, an application and documents must be submitted to the Immigration Bureau and finally approved by the Minister of Justice.

Since naturalization involves losing one’s foreign nationality and becoming a Japanese citizen, there are strict requirements regarding the application.

For example, the applicant must have reached the age of majority (18 years old) under Japanese law. They must also be of legal age under the laws of the country in which they currently hold nationality. There are also other requirements, such as having paid taxes properly and not having received any serious penalties during the period of residence in Japan before the naturalization.

Rules regarding the name after naturalization

If you are a Korean or other foreign national currently residing in Japan and have registered a common name (Japanese name) and are already using it, there is no problem, but you need to consider your name as a Japanese after naturalization.

There are two rules for determining your name after naturalization.

First, after naturalization, you must use your “Japanese name” because you will not be able to use your existing name.

What are the characters in a name, and what kanji characters cannot be used?

There are three types of characters that can be used in your “Japanese name” after naturalization: Kanji, Hiragana, and Katakana. However, Kanji characters are limited to those listed in the “Jyouyou Kanji Chart” and “Jinmei Kanji Chart. In other words, the rules are the same as those currently used by the Japanese when naming their children.

If the above rules are followed, current foreign names can be used as they are in katakana (Cruz/Tom), hiragana (Kuruz/Tom), or kanji (Kuruusu/Jumu). It is just that the existing alphabet cannot be used.

Those who have registered multiple aliases and used them in different ways will only be able to use the Japanese name they have decided upon after naturalization.

In addition, since “separate surnames for married couples” is not currently allowed in Japan, when a foreign national becomes a naturalized citizen, there are only two options: the foreign national may take the surname of his/her Japanese spouse, or the Japanese spouse may take the surname of the naturalized citizen.

In addition, it is not possible to use the same kanji as someone who is in the same family register. For example, suppose the Japanese spouse has a minor child whose name is Kazuya. If the naturalized citizen enters the family register of the Japanese spouse, he/she cannot use the kanji character “Kazuya” even if his/her name is “Kazunari.

However, even if the name is “Kazuya,” there is no problem if the kanji is different, such as ‘Kazuya’ or “Kazuya.

Summary

After naturalization, you can only use kanji, hiragana, and katakana in your “Japanese name” just like a Japanese person. In addition, you cannot use the same kanji as someone who is in the same family register as you after marriage.