Why The Mukoseki is Japan’s Deadliest Legal Trap

Why The Mukoseki is Japan’s Deadliest Legal Trap

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Child abandoned
Picture: freeangle / PIXTA(ピクスタ)
People without a family registry can die without access to essential services. Divorce law and Japan's koseki system explain why.

By now, it’s a familiar story in Japan: people left alone in their apartments, without any aid or nourishment, passing away.

Recently, an elderly woman died after she and her son subsisted off of salt and water for weeks. When they ran low on food and money, the man could not get help from the government. The president of the local autonomy eventually found the man greatly weakened but clinging to life. He revealed why he couldn’t seek help: he had no family registry. 

Similar stories crop up whenever people without a family registry die because of a lack of essential services. But in such a well-developed country, how is this sort of cruelty possible? The answer lies in a few minute but fatal holes in the law and the broader system surrounding Japan’s koseki, or family registry — the presence of mukoseki, the unregistered people without one.

Special thanks to Patron Tim Patrick of Japan Everday for providing feedback and corrections on this article.

What is koseki?

The koseki system dates all the way back to the 6th century Asuka Period, but it took its modern shape after the Meiji Restoration of 1868. Click To Tweet

First, we need to dive into what exactly koseki is, and why it plays such an important role in Japan.

Per the Japanese government, a family register is an official document that records and certifies the identity and family relationships of Japanese citizens. It contains an individual’s name, gender, birth date and birthplace, parental relations, spousal relations, and information about death, guardians, and inheritance. 

An example of a koseki from the Nagoya Meito Ward’s government website. https://www.city.nagoya.jp/meito/page/0000064593.html

It’s a simple, authoritative, and effective tool in Japanese society. According to Doshisha Law School professor Colin Jones, the koseki system is one of the reasons behind Japan’s low rate of litigation, a form of “freedom from the courts.” Issues with divorces, adoptive relationships, guardianship and custody, inheritances, titles to real estate, and much more can all be settled without the courts, under the authority of the family register.


The koseki system dates all the way back to the 6th century Asuka Period. However, it took its modern shape after the Meiji Restoration of 1868. The new government needed demographic information about the Japanese people in order to build an economic and military infrastructure to ward off the colonial west. The national koseki system became a way to collect information.

When the U.S. occupied Japan after World War II, American influence eliminated the “head of household” status and the ability to register more than two generations in one koseki. But pushback from Japan preserved the system as a whole.


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A video in Japanese describing the koseki system.

As a single document that provides official proof of identity and status, it does its job. It further provides a degree of freedom by allowing family matters to be settled out of courts.

But koseki does have major drawbacks. It can cause inconvenience and suffering to women and children. It discriminates against Japan’s ethnic Korean population. And when people slip through the gaps and become unregistered—it can kill them.

Small Complications Create Unregistered Citizens

There are a number of ways that unregistered people are born in Japan. But most commonly, it happens when a woman has a child with a new partner after a divorce. The law at play here is the now-infamous Article 772 clause 2 of the Civil Code:


A child born within 300 days of a legal divorce is presumed to be the child of the mother’s ex-husband.

That means that whenever a child is born within 300 days of a divorce, the birth certificate will automatically list the ex-husband as the father.

Masae Ido, the author of Mukoseki no Nihonjin (“Unregistered Japanese”), explains that this is just what happened in her case.

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Masae Ido’s book on Amazon.jp.

“Divorce mediation is long, and even after separation it can take a while for the divorce to get completed,” Ido told Tokyo Keizai. “I married my current husband and had a child, but the child was born within 300 days after the legal divorce.”

When she filed the birth certificate, the authorities told her that they could not recognize the child as the child of her current husband. Since she obviously could not file the birth certificate of her child with an unrelated man as the father, her child became mukoseki.

Mukoseki children can also result when parents are unable to file a birth certificate due to financial or environmental circumstances. But Ido’s scenario, is, frankly, not uncommon. Divorces in Japan take an average of 4-6 months and can sometimes take more than a year. That gives a lot of time for a child to be born within that extra 300 days after the divorce is concluded.

Ido took her issue to court, and after a lengthy battle, managed to register her child with her current husband. Her case resulted in a new exception that allows the woman to file a birth certificate without the ex-husband on it if a doctor confirms the time of conception. “My case became a precedent, but not a lot of people know about it,” Ido said.

Separate Ways: Why Joint Parenting After Divorce in Japan is So Rare

Becoming Unregistered Leads to Lifelong Disadvantages

Ido said that in working with many unregistered people, she has seen many cases of poverty and abuse. These often accompany difficult family circumstances that result in people being born as mukoseki. The children of sex workers or women with abusive husbands are particularly prone to this legal quagmire.

When people slip through the gaps and become unregistered, the koseki system can kill them. Click To Tweet

“Many of these people suffer from poverty, violence, and illness, and are unable to consult with anyone or receive any aid even when confronted with serious difficulties,” Ido said. “They are struggling to survive.”

“Often, the only way [for people without a registry] to get money is through an underworld job or turning to crime.”

Yokohama-based lawyer Minori Sato explains that the lack of a family register can block access to essential services. Without one, people may be unable to create a resident’s record, get a driver’s license, open a bank account, vote in elections, receive a passport or inheritance, or even marry.

A small but significant number of people live in this mukoseki status. An official government survey puts the number of unregistered people in Japan at 686. But Ido believes it is closer to and possibly well over 10,000 due to the survey’s 20% response rate and failure to count children under one year old.

Because the problems with koseki have emerged in public debate in Japan over the years, the system is less all-consuming than it used to be. Third-party access to koseki is more restricted. This means that employers cannot engage in direct discrimination against those without a koseki. However, without a resident’s record or a bank account, people can easily fall into unemployment. 

In fact, with the new My Number system, employment has gotten even more perilous. People who previously survived without a bank account by handling cash now have to submit their My Number to their workplaces, potentially resulting in them losing jobs.

The largest population in Japan without koseki is the Zainichi Korean population.

An Overhaul - Or Reform?

“Often, the only way [for people without a registry] to get money is through an underworld job or turning to crime.” Click To Tweet

Awareness about mukoseki has risen in Japan as Ido’s and a number of other books have been published over the years, exposing the problem. But politicians still need to act to solve the legal issues that create these potentially dangerous circumstances.

One recent step taken by the courts declared Article 733 of the Civil Code unconstitutional. The law previously prohibited women from remarrying for six months after a divorce. The courts have issued an amendment to shorten the remarrying period to begin 100 days after divorce.

In addition, Ido’s case permits women to register their children if a doctor can prove that she became pregnant after separation from her ex-husband. But these small changes still leave many scenarios where children might end up unregistered. And the Japanese government is not actively trying to make further changes to the koseki system or the laws surrounding divorce.

For people who realize they don’t have a registry, the Japanese government recommends consulting with a lawyer. The Ministry of Justice website suggests that an unregistered person can receive a koseki by presenting their birth and work registration to the local city hall. But of course, many people without a koseki will lack both of these. 

A more drastic solution would be to abolish the koseki altogether. Jones suggested in the Japan Times in 2016 that it could be on the table.  “The Justice Ministry published a report on all the ways in which My Number could serve as a source of Official Documents in lieu of koseki extracts,” Jones wrote.

“Perhaps this will serve as an opportunity to get rid of the archaic family rules entrenched in the koseki that cause many Japanese people—women and children in particular—pointless suffering and inconvenience.”

A smaller solution would be to thoroughly revise or abolish the aforementioned Article 772. In an age of DNA testing—and a society theoretically more progressive than the Meiji era—there should be no need to assume who a child’s father is. But Ido said that, despite her active efforts to campaign against the law, it remains unchanged.

“I believe this is a neglect—a form of abuse—of children by the state,” said Ido. “Children who are in need are left unassisted.” 

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Eric Margolis

Eric Margolis is a writer, translator, and book editor based in Nagoya. His investigative features on Japan have been published in The Japan Times, The New York Times, Vox, Slate, and more.

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