International marriages have been increasing in Japan.
 
(Mainichi Japan) January 24, 2011
 Japanese singer Ayumi Hamasaki recently married a man of Austrian  nationality. The Mainichi answers questions readers may have about  international marriages and nationality.
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Question: What is Japan's position on nationality when it comes to international marriages?
Answer: The Japanese Nationality Law states that "a Japanese national  shall lose Japanese nationality when he or she acquires a foreign  nationality by his or her own choice." As a result, unless the Japanese  national takes steps to obtain the nationality of their spouse, the  person retains Japanese nationality. However, in countries such as Iran,  when a couple marry, the wife is required to obtain the same  nationality as the husband.
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Q: In international marriages, which country's laws should the couple abide by?
A: When it comes to conditions for marriage, such as age, they abide  by their own country's laws. In Japan, that means the Civil Code, which  stipulates the age at which people can marry and bans practices such as  bigamy. Legal worker Yukio Enomoto, an expert on international  marriages, says that when the couple gets married overseas, they submit  to the procedures determined by that country, then, within three months  of their marriage, they are required to submit a marriage certificate to  a Japanese diplomatic office in that country or to the Japanese  person's legal domicile. If they don't do this, their marriage will not  be recognized in Japan.
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Q: Do marriage procedures differ from country to country?
A: In Japan a "report of marriage" is submitted to local authorities,  but procedures differ from country to country as marriage is often  closely connected with culture and religion. Some countries conduct  ceremonial marriages in which vows must be made at a government office,  and some conduct religious marriages at churches or temples. One  39-year-old Japanese woman who recently married a man from New York said  that at the government office in New York, she vowed to remain with her  husband for life. Another 37-year-old Japanese woman who married a man  from Bangladesh said she was required to convert to Islam.
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Q: How many people in Japan are in international marriages?
A: According to a demographic survey conducted in 2009, there were  34,393 marriages in which one of the couple was a foreigner --  accounting for roughly 5 percent of all marriages in Japan. Thirty years  ago the figure was around 1 percent, and international marriages have  gradually been increasing since then. In marriages where the husband is  Japanese, the wife is often from China or the Philippines, and when the  wife is Japanese, South or North Korea, the United States, and China are  the top countries for the husband's nationality.
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Q: What nationality do these couples' children take?
A: In Japan, if one of the parents is Japanese, the children become  Japanese nationals. In the United States, children born in the United  States acquire U.S. citizenship, and if a Japanese women in an  international marriage gives birth in the United States, her child  obtains U.S. citizenship. However, if a notice of retention of  citizenship is filed when registering the birth in Japan, the child does  not lose his or her Japanese nationality. In such circumstances, the  child acquires dual nationality, and he or she must choose which  nationality to take by the age of 22. (Answers by Mikako Shimogiri,  Lifestyle News Department)