Japanese Koseki & surname| The things you should know before getting married

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I am Japanese national who is trying to get married to a foreign national.

Should I change my surname or should I keep my Japanese name?

Are you or your partner Japanese and wondering whether one of you should change the surname after getting married?

To avoid any issues caused by changing surname, you have to understand Japanese Koseki system(Family registry) .

I myself is a Japanese national and  I wondered whether I should change my name or not when I got married. This article is about how Japanese koseki system will affect your life if you get married to foreign national. 

This article will make you understand how Japanese koseki system works and will affect you and your future. You will be able to decide whether you want to change your name or not reading this!

What is Japanese Koseki?

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First of all, you have to understand the Japanese Koseki system. What is Koseki?

A koseki (戸籍) is a Japanese family registry. Japanese law requires all Japanese households (known as “ie“) to report births, acknowledgements of paternity, adoptions, disruptions of adoptions, deaths, marriages and divorces of Japanese citizens to their local authority, which compiles such records encompassing all Japanese citizens within their jurisdiction. Marriages, adoptions and acknowledgements of paternity become legally effective only when such events are recorded in the koseki. Births and deaths become legally effective as they happen, but such events must be filed by family members.

A typical koseki has one page for the household’s parents and their first two children: additional children are recorded on additional pages. Any changes to this information have to be sealed by an official registrar.

The following items are recorded in the koseki. (Law of Family Register, (戸籍法), article 13.)

family name and given name
date of birth
date of records and causes (marriage, death, adoption, etc.)
names of the father and the mother and the relation to them
if adopted, names of the adoptive father and mother
if married, whether the person is a husband or a wife
if transferred from another koseki, the former koseki
registered domicile (honseki-chi)

Only Japanese citizens may be registered in a koseki, thus the koseki doubly functions as a certification of Japanese citizenship. It also guarantees the accuracy of Japanese passport. Non-Japanese may be noted where required, such as being the spouse of a Japanese citizen or the parent of a Japanese offspring; however, they are not listed in the same fashion as Japanese spouses or parents.


Therefore, Koseki works as your certificate of your Japanese nationality. If you are not Japanese national, you cannot register yourself to the Koseki system.

The options for your name if you get married to foreing national

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You have three options for your surname if you get married to foreign national.

  • Keeping your Japanese surname
    =Husband and wife retaining separate family names.
      (It is called “Fufu bessei.” )
  • Changing your name to your spouse’s name (It is called “Kaisei”)
  • You can also create a name like 

    First name + Maiden name + your spouse’s name (It is called “Fukugo sei”)

    However, you have to have a legitimate reason why you have to have the “Fukugo sei” name, and consult with family court in Japan.

夫婦別姓(Fufu bessei): husband and wife retaining separate family names

Under Japanese law, husband and wife retaining separate family names is not legally accepted. Therefore all the surnames of family members should be the same.

However, as foreign nationals cannot be registered on Koseki, it is legally accepted that Japanese citizen keeps his/her maiden name if he/she got married to foreign nationals, which means the couples retain separate family names. This is called “Fufu Bessei.”

The pro and con of Fufu Bessei (keeping Japanese name).

  • You do not need to change all the names which are registered to the services that you are using
  • You can take over the name of “Your Japanese House”
  • Marriage certificate to prove your relationship
  • It may be hard to prove that you are a couple on some occasions. You may be required to prepare marriage certificate
  • Your child will take over only Japanese family name on Koseki. He or she cannot share the same surname of the foreign national partner in Japan as his/her name is not on Koseki.*

*In case you need the child to keep both parents’ name, you may consult with family court, however, the procedure is not that simple. 

Example of Koseki:

LETO TANAKA (The head of the Koseki)Child: Lisa TANAKA

改姓(Kaisei): The pro and con of changing your name from Japanese to foreign one

  • You can appreciate the fact that you got married 
  • You, your spouse and  your child, all of the family members will share the same surname in Japan

  • You have to change your registered names for all the services that you are using
  • As it is accepted to use your maiden name at work, you do not have any problem at work however it may be a trouble when you have to prove your new name at work.
  • There are many occasions that you have to tell your surname in Japan. If your surname is long and complicated one for Japanese people, it may be hard to make people understand your name.  Right after getting married, you may enjoy telling the new name explaining to the people but if you have to keep doing that for the rest of your life, it can be a hassle. 

The time that you can change your surname is limited

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It is possible to change the name only within 6 months of your the marriage. All you have to do to change your name is to submit “姓の変更届(Sei no henko todoke).”

After the month, you may have to go to the family court to change the name. 

You’d better decide whether you want to change your surname to avoid the problem later

Therefore, I recommend you to decide whether you want to change your name or not within 6th months of your marriage.

Also, you may have choice to deal with your new name and maiden name with your passport in those way.

  • Fufu Bessei(Husband and wife retaining separate family names)
  • Same surname with your spouse
  • Fufu Bessei + showing spouse’s name on the passport with bracket()
  • Same surname with your spouse+ showing your maiden name on the passport with bracket()

I chose the 4th option, which I changed my name to my spouse’s name and printed my maiden name with bracket() on my passport. As bracket has not been recognized in the other countries, my name is counted as “First name + maiden name + Surname” in the USA where I live currently.

Hopefully you can find a best option with your name!