Who Can Request a Koseki? The Direct-Line Rule Explained
Published Updated By TADOROOTS Research Team
Perhaps you've found the town in Japan where your great-grandfather was registered. You'd like a copy of his family register, but then the questions start: Am I allowed to ask for it? Would my cousin be a better person to request it? What would the town office need to see?
If you're wondering about this, you're far from alone. The rules can seem strict at first, especially from outside Japan. Here is the reassuring part: if you descend from the ancestor in a direct line, the law already gives you the right to that register — the real task is showing your line on paper.
We're the research team at TADOROOTS in Tokyo. We read old Japanese family registers every day to build family trees, including for Nikkei families abroad. In this article you'll learn:
who can request a koseki without giving a reason, and who can't
why the old household registers often show great-uncles and aunts anyway
how descendants abroad show their line of descent
what to prepare before any request goes to Japan
Who can request a koseki without giving a reason?
Under Article 10 of Japan's Family Register Act, the people named in a koseki, their spouses, and their direct ancestors and descendants can request a copy without stating a reason. This applies to the older, closed registers too.
"Direct" means a straight line up or down:
Up: parents, grandparents, great-grandparents and further back
Down: children, grandchildren, great-grandchildren and further on
So a great-grandchild living in the United States, Canada or Brazil is entitled to the register of a great-grandparent who emigrated from Japan, just as a grandchild in Tokyo would be. Living abroad doesn't change the rule.
Who can't request one freely?
Relatives outside the direct line — such as siblings' lines, nieces and nephews, cousins, aunts and uncles, and in-laws — can't request a koseki freely. Under Article 10-2, other people may request one only with a specific legal reason, for example to confirm the heirs in an inheritance, and they must state and usually document it. Interest in family history alone does not qualify.
Two examples help:
Your cousin is not your direct ancestor or descendant, so you can't request your cousin's register for family-history purposes. But if you and your cousin share a grandfather, each of you can request the grandfather's register.
Your spouse's family is related to you by marriage, not by descent, so their registers belong to your spouse's line. Your spouse, or your children, can request them.
This is why it usually works best for the family to agree which relative's line the search follows, and who signs.
Will I see great-uncles and aunts in my ancestor's register?
Often, yes: a register made before 1948 was organized around the head of the household, so it can list your ancestor's brothers, sisters, and their spouses and children on the same pages. If your direct ancestor is named in that register, you can request the whole register, including those relatives.
The limit comes when a relative moved into a separate register — for example, when a younger brother set up his own household or a sister married into another family. That separate register is not your direct line, so it isn't freely available. In our experience, the main household register still shows a great deal about the wider family.
How do descendants abroad show their line?
A request from abroad needs documents that connect you, generation by generation, to the person in the Japanese register. The town office has to be able to see that you are a direct-line descendant.
The chain usually looks like this:
Your own birth certificate, naming your parent
Your parent's birth certificate, naming the grandparent
Each earlier generation's birth or marriage certificate, up to the person born in Japan
Translations into Japanese, with the translator's name
If a parent or grandparent has a current Japanese register of their own, the chain can be shorter, because that register already links to the earlier ones. Requirements can differ by town office, so it helps to prepare the chain carefully before anything is sent.
How is the request made from outside Japan?
From abroad, a koseki is requested by post from the town office of the family's registered home (honseki), in Japanese. Some practical points to know in advance:
Fees are 450 yen per current register and 750 yen per closed or older register, normally paid with Japanese postal money orders (teigaku kogawase), which are hard to get abroad.
Timing: each exchange by post commonly takes a few weeks, and each register tends to point to the next one.
The 2024 one-stop service doesn't help from abroad. Since March 2024, registers from anywhere in Japan can be requested at one town office, but only in person at a counter in Japan, for oneself, a spouse or the direct line — not by mail or through someone else.
How far back: the oldest registers generally available are in the 1886 (Meiji 19) format. The 1872 registers are sealed.
When a family works with someone in Japan, the request is still made on the written authorization (power of attorney, 委任状) of a direct-line descendant, with the chain of descent attached. The right to the records stays with the family.
One more point: a family tree is a record of your family's history. It doesn't replace legal procedures such as inheritance, which have their own requirements.
In summary
The people named, their spouses and their direct ancestors and descendants can request a koseki without giving a reason.
Cousins, nieces and nephews, aunts and uncles, and in-laws need a specific legal reason, and family-history interest doesn't count.
From abroad, the key task is a clear chain of documents showing your line, generation by generation.
If you descend from the ancestor you're looking for, the door is already open to you — it's a matter of walking through it step by step.
How TADOROOTS can help
We help families abroad turn their right to the records into a family tree. We work out which registers your line can request and from which town, help you assemble the chain of descent, and prepare the paperwork for the direct-line descendant's written authorization. Then we read the old handwritten registers and build a family tree with an English report. You can see how our step-by-step pricing works. We can work with you in English, Chinese, Korean or Japanese.
Frequently asked questions
Q. Who can request a koseki without giving a reason?
The people named in the koseki, their spouses, and their direct ancestors and descendants, such as parents, grandparents, children, grandchildren and great-grandchildren. This is set out in Article 10 of Japan's Family Register Act.
Q. Can a cousin request a koseki for family history?
Not freely. A cousin, like a niece, nephew, aunt, uncle or in-law, needs a specific legal reason under Article 10-2 of the Family Register Act, such as confirming heirs. Interest in family history alone does not qualify. Cousins who share a grandparent can each request that grandparent's register.
Q. Can I see my great-uncle in my great-grandfather's register?
Often, yes. Registers made before 1948 were organized around the head of the household, so brothers, sisters and their families can appear on the same pages. A separate register a great-uncle later set up is not your direct line, though.
Q. Does living abroad change who can request a koseki?
No. A direct-line descendant abroad has the same right as one in Japan. The difference is practical: the request goes by post, in Japanese, with documents showing the line of descent.
Q. What documents show that I'm a direct-line descendant?
Usually a chain of birth and marriage certificates linking each generation, from you back to the person born in Japan, with Japanese translations. Requirements can differ by town office.
Q. Can I use the 2024 nationwide one-stop service from abroad?
No. Since March 2024 registers can be requested at one town office for the whole country, but only in person at a counter in Japan, for oneself, a spouse or the direct line, and not by mail or through someone else.
Q. Can someone in Japan request the register for me?
Yes, when it is done on the written authorization (power of attorney) of a direct-line descendant, with the chain of descent attached. The right to the records stays with the family.
Q. My request was returned. Does that mean the record is out of reach?
Not necessarily. In our experience, a returned request often means the chain of descent wasn't clear enough or the request went to a different town office from the one holding the register.
