Married to a Japanese National? How International Marriage Is Recorded in the Koseki

If you marry a Japanese national, you will soon hear the word koseki (戸籍), Japan’s family register. City offices ask for it, the immigration office asks for it, and your spouse’s family may talk about “entering the koseki.”

Many foreign spouses are surprised to learn that they do not get a koseki of their own, and that their name does not appear in the register the way a Japanese spouse’s would. This article explains, from the foreign spouse’s point of view:

• Why you don’t have a koseki
• How your marriage is recorded in your Japanese spouse’s koseki
• What happens to surnames
• How your children are registered
• How the koseki differs from the resident record (juminhyo)
• What changes if you naturalize

Foreign nationals do not have a koseki

The koseki system applies only to Japanese nationals. It records a Japanese person’s birth, marriage, divorce, parent–child relationships, and death, and it also serves as proof of Japanese nationality.

As a foreign national, you are not registered in any koseki, even after you marry a Japanese national and live in Japan for many years. There is also no “koseki tohon” for a foreign spouse. If a Japanese office asks you for proof of your own birth or marital status, you will usually submit documents from your home country, such as a birth certificate or a certificate of legal capacity to marry.

How your marriage is recorded

A new koseki is created for your Japanese spouse

When two Japanese nationals marry, a new koseki is created for the couple, and both are listed in it.

In an international marriage, the situation is different. If your Japanese spouse was still listed in their parents’ koseki, a new koseki is created only for your spouse, with your spouse as the head of the register (筆頭者, hittosha). If your spouse was already the head of their own register, no new one is created.

At first glance, this new register looks as if your spouse were single, because you are not listed as a member. This often surprises couples, but it is normal.

Your details appear in your spouse’s “personal status” section

Your marriage is recorded in the personal status section (身分事項欄) of your Japanese spouse’s entry. The entry typically shows:

• The date of marriage
• Your name
• Your nationality
• Your date of birth

Your name is written in katakana, in the Japanese order (surname first, then given name), with a comma separating the two. For example, John Smith would appear as 「スミス，ジョン」. Nationals of countries that write names in kanji (such as China or Korea) can have their name recorded in kanji, but only if the characters are standard Japanese characters.

There is no official rule for how to spell a foreign name in katakana. David, for example, could be written デービッド, デイビッド, or デビッド. The spelling you write on the marriage notification is the spelling that goes into the koseki.

This entry is the official Japanese proof that you are married to a Japanese national.

Registering your marriage in Japan

If you marry in Japan

You and your spouse submit a marriage notification (婚姻届) to a municipal office. As the foreign spouse, you usually need:

• Your passport
• Your birth certificate
• A certificate of legal capacity to marry (婚姻要件具備証明書), usually issued by your country’s embassy or consulate in Japan
• Japanese translations of all foreign-language documents

Requirements differ by nationality. Some countries do not issue a certificate of legal capacity to marry, and other documents (such as a sworn statement) may be accepted instead. Check with the municipal office in advance.

Since March 2024, your Japanese spouse generally no longer needs to attach a koseki tohon to the marriage notification, because municipalities can now check koseki information with one another.

If you married outside Japan

If you married first under the law of your country or another country, your Japanese spouse must report the marriage to a Japanese embassy or consulate, or to a municipal office in Japan, within three months. A marriage certificate issued abroad, with a Japanese translation, is submitted with the report.

Reports made through an embassy or consulate are sent to Japan by diplomatic mail, so it usually takes about one to two months before the marriage appears in the koseki.

Surnames in an international marriage

Your Japanese spouse keeps their surname by default

In a marriage between two Japanese nationals, the couple must choose one surname. In an international marriage, the Japanese spouse keeps their own surname unless they take action.

Your spouse can take your surname

If your Japanese spouse wants to use your surname, they can file a notification of change of surname due to marriage with a foreign national (外国人との婚姻による氏の変更届):

• Within six months of the marriage: only a notification to the municipal office is needed
• After six months: permission from the family court is required

Your surname is then recorded in katakana (for example, 「スミス」) as your spouse’s legal surname in Japan.

What about your surname?

Japanese law does not change a foreign national’s name through marriage. Whether you can change your surname depends on the law of your country. If you change your surname under your country’s law, your spouse can file a request (申出) with the municipal office, or with a Japanese embassy or consulate, to update your surname in the koseki entry. You will also need to update your passport and residence card.

Many foreign spouses also register their Japanese spouse’s surname as an alias (通称, tsusho) on their juminhyo. Normally you must prove that you already use an alias in daily life, but when the alias comes from marriage to a Japanese national, municipalities generally accept it without that proof. The alias can then be used for banking, work, and other everyday matters in Japan.

Your children and the koseki

A child born to a Japanese parent acquires Japanese nationality at birth, whether the child is born in Japan or abroad. The child is recorded in the Japanese parent’s koseki and usually takes the surname shown in that register.

Points to keep in mind:

• Children born abroad: if the child also acquires another nationality by birth in that country (for example, in the United States or Canada), the parents must file the birth notification with a declaration to reserve Japanese nationality (国籍留保) within three months of the birth. If they miss this deadline, the child loses Japanese nationality.
• Dual nationality: a child with two nationalities must, in principle, choose one nationality by a certain age under Japan’s Nationality Act (generally by age 20 if dual nationality arose before age 18).
• Visa for the child: a child with Japanese nationality does not need a visa to live in Japan.

The koseki and the juminhyo are different

Many people confuse the koseki with the juminhyo (住民票, certificate of residence).

Since 2012, foreign residents with a residence card are registered in the juminhyo system. A household with a Japanese and a foreign spouse appears as one household, and you can get a juminhyo that shows both of you together. Immigration applications often require both documents: the koseki to prove the marriage and the juminhyo to prove that you live together.

Using the koseki for your visa

For the Spouse or Child of Japanese National visa (日本人の配偶者等), the Immigration Services Agency usually asks for:

• Your Japanese spouse’s koseki tohon, showing the marriage entry
• A marriage certificate issued by your country
• Your Japanese spouse’s juminhyo, showing all household members

If the marriage is not yet recorded in the koseki, you may submit a certificate of acceptance of the marriage notification (婚姻届受理証明書) together with the koseki.

Documents issued in Japan must be issued within the last three months.

As a spouse, you can request your Japanese spouse’s koseki yourself, even from overseas. See our guide: How to Get a Japanese Koseki (Family Register) from Overseas.

If you naturalize as a Japanese citizen

If you later naturalize (帰化) and acquire Japanese nationality, you will enter the koseki system for the first time. Generally:

• Because Japanese law requires a married couple to share one surname, you and your spouse will be listed in the same koseki, just like a couple of two Japanese nationals.
• There are two patterns. You can join your Japanese spouse’s koseki and use your spouse’s surname. Or you can create a new koseki with yourself as the head, under a surname you choose, and your spouse joins it and takes that surname.
• You choose your new Japanese name, which can be written in kanji, hiragana, or katakana.
• After naturalization is approved and announced in the Official Gazette, you must file a naturalization notification (帰化届) with the municipal office within one month.

From then on, you will have your own koseki entry, and you can obtain a koseki tohon that shows you as a member.

Divorce and the koseki

If you divorce, the divorce is recorded in your Japanese spouse’s koseki. If your spouse had changed their surname to yours, they can return to their former surname by filing a notification within three months of the divorce.

For your residence status, a divorce or the death of your spouse must be reported to the Immigration Services Agency within 14 days, and you may need to consider changing to another status of residence.

Summary

• Foreign nationals do not have a koseki, even after marrying a Japanese national.
• Your marriage is recorded in your Japanese spouse’s koseki, in the personal status section, with your name, nationality, and date of birth.
• Your Japanese spouse keeps their surname unless they file to take yours (within six months, without court permission).
• Your children with Japanese nationality are recorded in the Japanese parent’s koseki.
• Your juminhyo shows you and your spouse as one household, unlike the koseki.
• If you naturalize, you will be listed in the koseki together with your spouse.

This article provides general information and is not legal advice. Procedures may vary by municipality and by nationality, so please check with the relevant office before applying.