[Question] Upon marriage to a Japanese national, are there going to be any changes in my “family name” and “nationality”?

[Answer]
(Nationality) You nationality won’t change automatically with marriage to a Japanese national.

(Family Name) Whether or how your family name changes depends on the requirements in your country’s international law. Namely, 
①which country’s law will be used in the event you marry a foreign national, and 
②what the chosen law says about your family name after marriage.

[Question] What happens to the family registry, family name, residence registration and nationality of Japanese nationals who marry foreigners?

[Answer]
<Nationality> According to the Nationality Law, marriage to a foreigner does not cause the Japanese spouse to lose their nationality. In cases of Japanese women marrying foreigners, they can sometimes acquire the nationality of their husbands, depending on the laws of the husbands’ countries. In some cases, this acquisition is automatic, in which case the Japanese wife is temporarily a dual citizen, and in other cases she must apply for it, in which case acquisition of foreign citizenship can result in the loss of her Japanese citizenship.
<Family Registry> A Japanese national who marries a foreigner is registered in a new, individual family registry, with the fact of marriage to a foreigner noted in the personal reference box.

<Certificate of Residence> Households composed of Japanese nationals and their foreign relatives are all listed together on the Certificate of Residence. 

<Family Name> In general, marriage to a foreigner does not cause the family name of the Japanese spouse to change. If the Japanese spouse wishes to adopt the foreign surname, this can be accomplished by applying to the local municipality within six months of the marriage. Even if more time has elapsed, it is still possible to adopt the foreign spouse’s name by pleading to the family court.

For details, please see Civil Affairs Bureau/Justice Ministry HP.