Doing Japan's Choice of Nationality Procedure

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Japan has a procedure called 国籍選択 {kokuseki sentaku} (Choice of Nationality). It was created with the revision of the Japanese nationality laws to address the issue of involuntary multiple nationality acquisition by Japanese — usually those who are minors that received citizenship from a new world country in the Americas such as the United States via jus soli (nationality based on where you were born, sometimes called "birthright nationality"): Japanese-Americans and Japanese-Canadians, for example.

However, it can also apply in other circumstances, such as if you acquire another nationality involuntarily (meaning, you did not directly apply for it or naturalize) — such as through marriage to a person from a country that does not separate nationality with marriage (called jus matrimonii) or religion. It can also happen when somebody acquired citizenship after birth due to the revision in the Japan Nationality Law in 1985 that allowed people to inherit Japanese nationality from their mother as well as their father; this paperwork procedure is not considered naturalization and is called 国籍取得 {kokuseki shutoku} (nationality acquisition). This is how the current leader of Japan's Democratic Party (民進党 {Minshintō} / DP), Renho (村田蓮舫 {MURATA Renhō} née 謝蓮舫 {XIÈ Lián-făng}), acquired Japanese nationality after being born with nationality from Taiwan / the Republic of China (台湾／中華民国 {Taiwan / Chūka-minkoku}).

Who must do it?

Japan's Choice of Nationality procedure must be done in three different circumstances:

1. Minors — in Japan's case, those under the age of twenty (20), not eighteen (18) — born on or after 1985, who have dual-nationality or multiple nationalities, obtained by any method or reason, where one of the nationalities is Japanese, who become adults. It must be done within two years after being recognized as an adult in Japan, so as of 2016 law, by the time one becomes 22.
2. Adults with Japanese nationality who for some reason acquire an additional nationality involuntarily (such as through marriage), within two years of acquiring the additional non-Japanese nationality.
3. Foreigners who naturalize to Japan yet are prohibited from removing their non-Japanese nationality. Although it is a UN Human Rights violation (Article 15), not all countries allow their citizens to renounce their nationality.

One can do the procedure as early as fifteen (15) years old, but those who are a minor (by Japan's legal standards) need the permission of their parents or legal guardians.

Older J-diaspora are grandfathered and exempt

Those who are born prior to 1985 are grandfathered in under the previous nationality laws and do not need to do the Choice of Nationality. They can, but they are not legally obligated to. Thus, those Japanese nationals who acquired Japanese nationality involuntarily through birth and are currently 32 years old or older in 2016 are legally multiple/dual national Japanese and do not need to do the Choice of Nationality. Technically, from the Japanese government's point of view, however, these people are assumed to have chosen Japanese nationality.

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Recently, Japan has changed its laws to allow eighteen (18) year old Japanese nationals the ability to vote, even though they are technically still minors by Japanese law. However, there is discussion about unifying all the laws referencing the age of majority in Japan from twenty (20) to eighteen (18). If this happens, then one will be able to legally drink alcohol and smoke tobacco two years earlier. It will also mean, though, that a dual-national etc. will have to make their Choice of Nationality by the age of twenty (20) rather than 22.

How is The Choice actually done?

1st Japanese "Embassy" in the District of Columbia, 1860

The Choice procedure is done by submitting a form called the Choice of Nationality Form (国籍選択届 {kokuseki sentaku todoke}) to the local ward office or city hall within Japan where the Japanese national has their resident registration (住民票 {jūminhyō}) at. For Japanese nationals living overseas, it is done at a Japanese consulate or embassy. Sometimes, in very big countries with large spread out Japanese diaspora (such as the United States), Japanese diplomatic operations overseas set up temporary facilities once or twice a year for this sort of paperwork. For example, in 2016 Japan only had consulates & embassies in sixteen (16) places in the territories of the United States of America:

• Anchorage, Alaska
• Los Angeles, California
• San Francisco, California
• Denver, Colorado
• Washington, D.C. (embassy)
• Miami, Florida
• Atlanta, Georgia
• Hagåtña, Guam
• Honolulu, Hawaii
• Boston, Massachusetts
• New York City
• Saipan, Northern Marianas
• Portland, Oregon
• Nashville, Tennessee
• Houston, Texas
• Seattle, Washington

Periodically, a Japanese consulate in America in a relatively nearby city or state may set up a "citizen service station" in a place without convenient Japanese consulate representation to assist Japanese nationals with legal matters.

You don't really have a "choice"

When in doubt, choose "C".

The actual form you are to fill out doesn't really give you a choice. It is an formal signed written declaration that you choose Japanese nationality and you will get rid of your other nationalities. The actual declaration part of the form, pre-filled and not modifiable, states:

国籍選択宣言 {kokuseki sentaku sengen}

日本の {Nihon no} 国籍を {kokuseki o} 選択し、 {sentaku shi,} 外国の {gaikoku no} 国籍を {kokuseki o} 放棄します。 {hōki shimasu.}

which roughly translates in English to:

Declaration of Nationality Selection

I choose the nationality of Japan, and will give up my [non-Japanese] nationalities.

The cost of doing the procedure to choose your nationality is free in Japan: ¥0, and if you're 15 years old or older but still a minor in Japan, you need the permission of your legal guardian(s). You don't have to wait until you're an adult to choose. If you are submitting the form to an overseas embassy, you will need to also submit a recent official copy of your Japanese family register.

How is the Choice of Nationality reflected on official paperwork?

Once you submit the paperwork to the authorities, a new 身分事項 {mibun jikō} (personal event) is created in your 戸籍 {koseki} (Japanese family unit register) with the following fields:

Copy (複写 {fukusha}) of a 戸籍謄本 {koseki tōhon} (official copy of a Japanese family unit register)

There may also be a 外国国籍喪失 {gaikoku kokuseki sōshitsu} (Foreign Nationality Loss) field in here depending on the foreign nationality
国籍選択 {kokuseki sentaku} (Nationality Selection)	【国籍選択の宣言日】[kokuseki sentaku no sengen-bi] (Nationality Selection Declaration Date)
	If submitted to a municipal office (市区町村役場 {shikuchōson yakuba}) not at one's registered domicile (本籍 {honseki})	【送付を受けた日】[sōfu o uketa hi] (Date Submission Received)
		【受理者】[jurisha] (Recipient)

In theory, there could possibly be more than one of these events in this section. For example, if you selected Japanese nationality then involuntarily obtained yet another foreign nationality, you would do the Choice of Nationality procedure within two years of becoming aware of the involuntary / inadvertent foreign nationality acquisition.

What do you do after "choosing" Japanese nationality?

Americans need this to prove
they gave up their U.S. nationality

The next step is to fulfill your written and signed obligation to give up all your foreign nationalities. If you are able to legally renounce your nationalities, you are obliged to do so as part of your declaration. This usually involves a procedure for renunciation that is done at an embassy or consulate in Japan, not actually in the country of that nationality.

In the case of Chinese Taipei, which has no formal diplomatic relationship with Japan, you would do it at the main "Taipei Economic and Cultural Representative Office in Japan" or one of its branch offices.

Once you have renounced your nationality, you should receive a certificate and/or official paperwork (or a voided foreign passport noting the reason for the cancellation being loss of nationality). In the United States, this is called a Certificate of Loss of Nationality. Take this paperwork, along with a Japanese translation (it does not have to be done by a professional), with identification, to the place that handles the administration of your 戸籍 {koseki} (Japanese family register) — usually a 区役所 {kuyakusho} (ward office) or a 市役所 {shiyakusho} (city hall) close to where you are registered to live in Japan, and tell them you wish to complete and submit a 外国国籍喪失届 {gaikoku kokuseki sōshitsu todoke} (loss of foreign nationality form). Upon doing this, there will be a entry in your register that looks like this and has the following fields:

Portion the of 身分事項 {mibun jikō} (personal matters) section of a 戸籍謄本 {koseki tōhon} (official copy of a Japanese family unit register)

There may also be a 国籍選択 {kokuseki sentaku} (Nationality Choice) field in here depending on the foreign nationality
外国国籍喪失 {gaikoku kokuseki sōshitsu} (Loss of Foreign Nationality)	【外国国籍喪失日】[gaikoku kokuseki sōshitsu-bi] (Date of Loss of Foreign Nationality)
	【喪失した外国籍】[sōshitsu shita gaikokuseki] (Foreign Nationality Country Name)
	【届出日】[todoke-bi] (Notification Date)
	If submitted to a municipal office (市区町村役場 {shikuchōson yakuba}) not at one's registered domicile (本籍 {honseki})	【送付を受けた日】[sōfu o uketa hi] (Date Submission Received)
		【受理者】[jurisha] (Recipient)

Americans who relinquish their U.S. nationality …by taking an oath, affirmation or other formal declaration to a foreign state or its political subdivisions… such as by doing the Japanese Choice of Nationality procedure should have a notation similar to "Sec. 349 (a) (2) INA" in their cancelled U.S. passport and on their CLN. This is slightly different than those who naturalize to Japanese, which will have a notation similar to "Sec. 349 (a) (1) INA" — note the difference between the number one (1) and number two (2) in parenthesis. However, both methods are considered and treated as "relinquishment", not "renouncement", by U.S. law and the IRS tax authorities.

The second meaning of "give up nationalities"

If you can't renounce…

If you are legally unable to give up your foreign nationalities, then you must endeavor to never use the privileges or rights that that nationality would give you. Depending on the country, this may be things such as:

• give up voluntarily possessing and/or renew a passport for a non-Japanese, or use that passport for travel or visas
• give up using rights related to suffrage: participate in politics (vote, run for office, support politicians or parties)
• give up working or living in the country without getting permission as a foreigner using a visa ("freedom of abode")
• give up working in a job only available to citizens of that country (ex. military, government, public servant, police, pilot or captain)
• give up exercising any other privilege or right that would only be available to a national (financial, social welfare, etc.) who was in the same position as you

There may be cases where using the nationality is unavoidable. For example, most countries require its nationals to use their own passport to enter and leave the country, even if you have more than one passport. If may be impossible to return or illegal to dispose of or destroy your current passport; you will simply have to wait up to ten (10) years for the passport to naturally expire. Additionally, because you are still technically a national of that country, you may end of being on the hook for duties and responsibilities related to its laws (such as taxation or military service or judicial service), even if you are not physically in that country's territory anymore.

In particular, the Japanese nationality law makes it clear that if you attempt to work for the government on a foreign country (for any public civil servant position that is limited to nationals of that country) while abstaining from using any foreign nationality, you can be stripped of Japanese nationality (Article 16) by the Minister of Justice.

How do I know whether I should renounce or "give up / abandon" my foreign nationalities?

If you have naturalized, you will be told, either orally and/or paperwork instructions containing check marks beside the procedures that you should do, whether or not a nationality renunciation procedure exists for your foreign nationalities.

Additionally, your case worker will have looked into the legal procedures for your country and will have determined if a procedure exists for renunciation. The Oath to Renounce that you sign and address to the Japanese Minister of Justice will contain two words separated by a mid-dot and one of them will be circled or crossed out: 放棄 {hōki} (give up / abandon)・離脱 {ridatsu} (renounce / relinquish); and the country/countries the selected word applies to will be written above the underline. This will indicate whether you made a legal oath to renounce your non-Japanese citizenship(s) and turn in evidence within two (2) years, or perform the Choice of Nationality procedure.

Can you do the Choice of Nationality instead of formally renouncing / relinquishing non-Japanese nationalities?

An interesting trait of the Choice of Nationality process is that they will let any Japanese national that has a nationality other than Japanese do it, even if they don't legally need to do it. For example, those born before 1985 or those who are supposed to renounce their foreign nationalities (because they are naturalizing and a renunciation procedure exists for the countries) are not required to do the procedure.

This is because the 市区町村役場 {shikuchōson yakuba} (municipal office) or the 在外公館 {zaigai kōkan} (overseas diplomatic mission) is simply in charge of ensuring that you meet the primary requirements to accept the paperwork to add a identity matter to your family register:

• you're Japanese
• you have another nationality
• you are old enough or have permission to do the process

A substitute's only recognized if the recipe permits.

If you are an American or Canadian and you naturalize to Japanese, you will be told by the Ministry of Justice, both orally and in writing and via having you sign an oath, that you need to renounce your nationality. However, it is still possible to do the Choice procedure even though it is legally possible for you to relinquish or renounce your nationality.

Nevertheless, doing the Choice procedure will not create the 外国国籍喪失 {gaikoku kokuseki sōshitsu} (loss of foreign nationality) entry in the 身分事項 {mibun jikō} (personal matters) section of your 戸籍 {koseki} (family register), which is what is what the 法務省 {hōmushō} (Ministry of Justice) will want to see if they decide to check if you followed through and completed the conditions in the naturalization law and your oaths or what you declared in your Choice declaration.

The Choice Procedure is not the final step if it is possible to legally renounce or relinquish your nationality; it is not a substitute for legally giving it up.

Can I just do the Choice Procedure if Renouncing/Relinquishing is too hard or expensive?

The hard part's not getting
a new nationality, but getting
rid of the old nationality.

How difficult it is to do the other half of the naturalization process, remove your other nationality, depends on those countries. If it's legally impossible (that is, forbidden by the law of that country or there is no legal method), then Japan offers a compromise, because it wants its naturalization process to be equally available to all non-national immigrants.

What happens, though, if it's not impossible, but just difficult or arduous? What happens if it takes a long time to do? Requires a very long time to process and is difficult to schedule and make appointments? Requires difficult to obtain or complete paperwork? Contains punitive or other measures to discourage it? Requires you to travel (perhaps multiple times) to a country that is far away? Is vindictive in that it future interaction with that country may be problematic? Requires you to pay an extraordinary fee or pay an extraordinary amount of "taxes" or a penalty such as an "exit tax"?

Unfortunately, the neither the Choice of Nationality Procedure nor the Naturalization process give preference or leniency for these matters. I have read things on the internet (!) where some people have claimed they they received a "special exemption" from renouncing because they were from America and "they made too much money"; when I confirmed with officials at 九段下 {Kudanshita}, however, they were skeptical. Heavily paraphrasing, he said,

We do not give people an exemption because they pay too much tax. If anything, it makes more sense that we'd be less likely to be lenient on somebody who was wealthy, because they can afford it and have the means to do it. I promise you that no matter how much money this person has, there are wealthier people who have naturalized and they did not receive any breaks. We cannot encourage people to skip inconvenient parts of the law simply because of their ways and means.

When you consider that one of the richest men in both Japan and the world, billionaire Masayoshi Son (孫正義 {SON Masayoshi}), claimed in his biography that he was not able to receive preferential treatment, this makes sense.

If your other nationalities don't allow dual citizenship either, is renouncing them necessary?

Although not diplomatically recognized
by Japan, Taiwan does have a way to
renounce its nationality.

Most of the countries in the world do not allow for people to voluntarily hold multiple nationalities. And even more countries in Asia don't allow for multiple nationality, and the nations from which, on average, have represented over 90% of the group of people that have naturalized to Japanese don't recognize dual nationality either.

So, all these people need to do is voluntarily naturalize to Japanese or voluntarily select Japanese nationality, and their previous nationality automatically becomes null and void, correct?

Not really.

At the very minimum, you may have to notify the governments of your non-Japanese nationalities that this event has occurred. Government bureaus around the world do not periodically read the government publications such as the Official Gazette (Japan) or the Federal Register (United States) to determine who has acquired or lost nationality. Even if they tried, they probably wouldn't be able to confirm it because the names were ambiguously transliterated into a foreign script (Japan) or the data may be known to be not 100% reliable with typos, omissions, or duplicates (United States). Countries that naturalize people, transforming them into their own citizens, are under no obligation to tell other countries that they have done this. A country can attempt to ask or confirm if a person possesses a nationality, though, but this is guesswork and time consuming. The policy is "Ask. Don't Tell."

Most countries have to be extremely careful not to accidentally make somebody stateless due to United Nation's conventions and because having a nationality is a human right. Thus, countries will only remove the nationality from somebody when they have seen solid proof that the person possesses another nationality. And this proof usually has to be provided by the person in question, unless a formal investigation is occurring. The proof has to be so good that a passport is usually not considered to be good enough proof of current (← keyword) nationality.

In recent news, the current Democratic Party of Japan (民進党 {Minshintō} / DP)'s leader and member of the House of Councillors (参議院 {sangiin}), "Renho" (村田蓮舫 {MURATA Renhō}), discovered this the hard way when the press discovered that neither she nor her parents had informed the government of Taiwan, ROC, that she had acquired Japanese nationality. Being a lawmaker that is legally connected to two different sets of (often incompatible) laws is scandalous and problematic.

What do you do if you don't choose Japanese nationality?

In Japan, burning or defacing the national flag (for protest, etc) is allowed (Article 21).
But burning other countries' flags is illegal.

If you don't choose your Japanese nationality, then the alternative is to formally lose your Japanese nationality, which is done with a separate form:

国籍喪失届 {kokuseki sōshitsu todoke} (Forfeiture [Relinquishment] of [Japanese] Nationality Form)

This procedure is done when you have deliberately or voluntarily did something to lose your Japanese nationality. For example, when a Japanese adult takes U.S. nationality through naturalization.

The definition of what constitutes forfeiture/relinquishment of Japanese nationality is Japan's Family Register law (戸籍法 {koseki-hō}), Articles 103 & 105.

国籍離脱届 {kokuseki ridatsu todoke} ([Loss] Renouncement of [Japanese] Nationality Form)

This procedure is done when you let go of your Japanese nationality due to other reasons, such as the involuntary acquisition of a non-Japanese nationality through birth in a jus soli (birth citizenship by soil/territory) country like most in the Americas or marriage (jus matrimonii) — though there are few, if any, nations in the 21st century that confer nationality simply by marrying somebody; marriage however often does simplify and make naturalization easier, but it does not make it automatic nor guaranteed.

The definition of what constitutes renunciation of Japanese nationality is defined by Japanese Nationality Law (国籍法 {kokuseki-hō}), Article 13.

The cost of doing the procedure to lose your nationality is free in Japan: ¥0.

Like the Choice of Nationality form, you can do these procedure as early as fifteen (15) years of age, but Japanese minors need the permission from their legal guardians.

Although the ability of a Japanese national to divest themselves of the nationality is an explicit constitutional right (Article 22), a prerequisite for doing the above procedures is you must show current proof of possessing a non-Japanese nationality (and providing Japanese translations of this official foreign paperwork). This is because Japan and most other countries of the world have ratified the UNHCR Conventions on the Reduction of Statelessness. The United States is an exception in that it will let overseas American citizens renounce and be stateless (an American cannot renounce on U.S. territory except during official times of war).

Are there any penalties for not choosing?

Don't turn your back on disaster or news.

There are no fines or imprisonment specified for failing to choose a nationality by two (2) years after being a Japanese adult with involuntarily acquired non-Japanese nationality (as of 2016, this means before turning the age of 22).

However, the nationality law does stipulate that they can remove your Japanese nationality if you don't choose by the law's deadline.

According to the Japanese Nationality Law, the procedure for removing your Japanese nationality for failing to choose is as follows:

1. First, the Ministry of Justice will try to contact you directly.
2. If they are unable to reach you directly (most likely, as they probably don't have your address, email, or phone number on record if you are living outside of Japan), they will post a notice to you in the 官報 {kampō} (Official Gazette) warning you contact the Ministry of Justice within one month. As most people don't make it a habit of reading the Japanese Official Gazette, you will most likely miss reading about or learning about this notice.
3. Unless they have reason to believe you have a good excuse for being tardy and not responding (ex. natural disaster, calamity or war in the area where they believe you are), they can remove your Japanese nationality if you fail to respond and choose within one month of the written publicly published notice.

If you miss the one month deadline however, you still have one last chance to get your Japanese nationality back:

• If you legally renounce / relinquish your foreign nationalities within one year after losing your Japanese nationality due to failure to choose in time, they will restore your Japanese nationality.
• If, in the judgement of the Ministry of Justice, there's a good external reason (ex. war, natural disaster, calamity etc.) why you can't renounce or relinquish your foreign nationality, then the deadline for legally relinquishing / renouncing your foreign nationality will be extended to one month past the time when they believe you are able to reasonably legally remove your foreign nationalities.

As of 2016, the Ministry of Justice has never posted a notice in the government's Gazette, but they have warned people of tardiness by contacting them directly via postal mail.

What happens if you choose Japanese nationality but then don't give up your foreign nationality even though you can?

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The truth is, nobody knows for sure with respect to the Choice Procedure because it's never been tested or challenged by either side.

Message boards in the English internet are full of stories from the Japanese diaspora (Japanese-Americans, Japanese-Canadians, etc) about how what you should do is make sure you get a ten year passport (the red one) after you become an adult (twenty in Japan) then do the Choice of Nationality procedure and "choose Japan" and then do nothing. If you're caught still possessing both after a considerable amount of time, they say, just give the excuse to the (most likely) airport immigration officer that "you haven't gotten around to it", or some similar excuse.

Even if an immigration officer never asks you about it, you will eventually have to confront being asked about it if you attempt to apply for renew your Japanese passport after you made The Choice: the application form has a question asking about the possession of dual nationality and asks specifically how you obtained it, as well as warning about fines and imprisonment penalities for lying on the government paperwork.

According to the Japan's Nationality Law, Article 14 Paragraph 2, the phrase 『国籍選択』"kokuseki sentaku" ("declaration of choice") is a euphemism/definition for the renouncing / depraving and swearing to be a Japanese national. In theory, if the Ministry of Justice were so inclined, they could argue that a person who merely signed a form without actually doing anything about their foreign nationality didn't actually do "the choice", which would mean the procedures for removing Japanese nationality from somebody who fails to do the whole Procedure within the allotted time.

Misinfo: you will never get caught nor will they enforce single nationality if you cut corners

Spending a life avoiding getting caught
is a stressful way to live.

I have read several theories, often accompanying advice among young Japanese dual nationals faced with the Choice of Nationality but trying to have the best of both worlds, that it is okay to hide or ignore your lack of decision based on three theories:

1. There is no punishment such as a fine or imprisonment, therefore the laws are toothless and without meaning.
2. It is too difficult for the government to detect who has dual nationality, and/or there is no way for the government to ask other governments if a person possesses a nationality.
3. The government is intentionally not enforcing single nationality rules because they are afraid they will not choose Japan, and they'd rather have a dual national than no national at all.

It is true that there is no penalties such as a fine or imprisonment for not doing properly doing either the Declaration of Choice or its naturalization procedure properly. However, just because there is no defined penalty (yet) does not mean it's not illegal. Both mandates for giving up one's nationality when one chooses Japanese nationality (either through naturalization or through the Choice procedure) is defined and codified in law. When something is written in law, and you do not something not in accordance to the law, that is by definition illegal.

While there is no defined penalty in the form of a fine or imprisonment, the government does have a mechanism for removing your Japanese nationality if they determine that you do not do either the Choice of Nationality or the Naturalization procedure in Good Faith and they know you have more than one nationality: Administrative Denaturalization, which is a fancy way of saying they are removing nationality from you, after the fact, because you never actually properly acquired or kept it. This is sort of like a marriage annulment, which is different from a divorce, in that the "marriage" was discovered later to not be legitimate.

Once upon a time, when all of the naturalization records were on paper or in various incompatible digital formats (part of the national My Number and family register systems involved unifying all the character encoding schemes used by local governments using Unicode with IVS), decentralized across the country, discovery of family registers whose entries were inconsistent or out of date could not be done automatically. Starting just last year, however, it is now possible to discover missing or inconsistent records in automated batches using a database procedure language; what would have taken hundreds of thousands of man hours in the 20th century can now be done, thanks to computers, in seconds.

The last theory I've heard is that the Japanese government is well aware that people are not properly giving up their nationality, but they're choosing to intentionally not do anything about it because they don't want the worldwide population of dual or multinational overseas Japanese to decrease. Pop theories as to why they would do this range from: the economic value that global expat migrants provide back to the homeland, the need to keep the official Japanese national population from dropping further (via any means possible), and simple explanations regarding ethnic pride and loss of face.

To me this sounds like rather dangerous wishful thinking. It's like saying that the reason almost no Americans overseas get caught for not filing annual income tax forms is because the United States' government is afraid that too many people will give up their U.S. citizenship. Judging from the number of Americans that are giving up up since they started making new laws to detect people not in compliance, it doesn't seem to bother the American people a bit.

There are very rough estimates, with wide margins of error, of anywhere from 600,000 to 700,000 Japanese nationals who hold more than one nationality. Of those, the vast majority are exempt from doing the Choice procedure because they were born before 1985. They are a smaller group than the foreigner population in Japan. Compared to many other Asians overseas, their numbers are dropping rapidly. Most of the Japanese diaspora has entered the  4th or 5th generation and their parents, whose connections to Japan and its language are often weak or non-existent, often don't bother securing Japanese nationality for their children; they are usually too assimilated into their host cultures to re-immigrate into Japanese society. Thus, most of them contribute little to nothing back to the Japanese economy except for perhaps an occasional vacation to Japan and an extended work/stay during their gap years before or after completion of higher education.

Recently, many countries around the work (Denmark, Austria, and Canada being in the news recently) have begin to assert their sovereign right to revoke their nationality from a person if they possess more than one — a strict interpretation of U.N. based human rights (Article 15) which state that every human is entitled to "a" (one) nationality, but not necessarily more than that. Furthermore, the vast majority of the population only has one nationality; they do not feel much sympathy for those, who due to privilege and circumstance, are are able to "forum shop" between different countries, overriding the democratic principle of every person under the same set of laws, in it together for society.

For those born overseas who reject the actual meaning of nationality — a legal tie to a nation-state government and its laws — and use it as a token of ethnic identity or a symbol of an emotional tie to both parents, the loss of a nationality that they don't actually use is probably of little real non-emotional consequence. However, for those that actually use their Japanese nationality, such as people who have a permanent life in Japan, it is probably better to choose your nationality, rather than find yourself in the bad situation of having a government "choose" it for you.

How many Japanese renounce or relinquish their nationality?

The procedure and law for Choice of Nationality wasn't created until 1985. Those born after this date didn't have to make a choice of nationality until two years after they were recognized as an adult in Japan. 1985 + 20 + 2 = 2007. Thus, people who relinquished their Japanese nationality for another foreign nationality is still a new thing, less than a decade old at the time this post was written (2016). The numbers are very low for renouncing one's Japanese nationality (due to naturalizing to another nationality) as well.

The terms "relinquishment" for 喪失 {sōshitsu} & "renunciation" for 離脱 {ridatsu},
even though they're not exact translations, roughly corresponds to the U.S. notions of relinquishment (involuntary) and renouncement (voluntary).

licensed from CartoonStock Ltd.

Japan is the reverse of the United States when it comes to publishing personal data about those who change nationality. In Japan, your date of birth, your home address, and your (former) name — converted to Japanese syllabet (仮名 {kana}) or sinograms (漢字 {kanji}) — are published in the Official Gazette (官報 {kampō}) for the Japanese government. The United States couldn't possibly publish all the names because there are too many. However, they do have a "name & shame" list where the publish the full names of those who either relinquish or renounce their U.S. citizenship every quarter, in the U.S. Federal Register that was created in the nineties due to the belief that the only reason most Americans would give up their precious United States nationality was because they were attempting to avoid paying their obligatory tax duties. The arduous annual procedures and paperwork expat Americans have to report and file for federal and state income tax every year, combined with the threat of fines related to FBAR compliance tardiness and mistakes, as well as extraterritorial enforcement and vetting via FATCA, has meant that the quarterly list has grown so large that it requires fancy formatting for the web version of the publication, and it may start to swell the size of the printed version of the U.S. Congress' publication.