Japanese Family Register (Koseki) Retrieval & Translation
If you have Japanese ancestry, Japan's family-register system may contain official records that document your family line. Yuzo Ochiai of EAI helps clients overseas identify, retrieve and translate eligible koseki records in Japan without needing to travel there themselves.
What is a koseki?
Japan's family-register system records legally recognised family relationships and major civil-status events.
A koseki (戸籍) is Japan's official family register. It can record births, marriages, divorces, adoptions, parent-child relationships and deaths, making it one of the most important official sources for documenting a Japanese family line.
Family research can involve several linked registers. A current register may point to an earlier register, and older closed or pre-reform registers may reveal earlier generations or branches of the family. Followed back through the chain, koseki research commonly reaches four to six generations, into the 1870s and 1880s when the modern system began.
The records are held by more than 1,500 municipal offices across Japan, each responsible only for families registered in its own area, and are issued in Japanese. Two pieces of information unlock everything: the honseki (本籍, the family's registered domicile) and the correct kanji for the family surname. For someone overseas, finding these, proving the family relationship and managing the application is the difficult part. This is where Yuzo helps.
The main terms to know
- 本籍 · Honseki
- The family's registered domicile, the address that determines which municipal office holds the records. One of the two keys to any retrieval, together with the surname kanji.
- 戸籍謄本 · Koseki tōhon
- A full certified copy of the entries contained in a family register.
- 除籍謄本 · Joseki tōhon
- A copy of a register that has been closed after all members were removed from that register.
- 改製原戸籍 · Kaisei genkoseki
- An earlier form of a family register retained following revisions to the family-registration system.
Who needs a koseki?
Most enquiries come from people of Japanese descent living overseas, or from families who need official evidence of a Japanese family relationship.
Why request your koseki now, not later
These records will not wait indefinitely. Three practical reasons families choose not to put this off.
Retention limits are real
Closed registers are kept for 150 years, and the earliest Meiji-era registers are already approaching the end of their statutory retention. Yuzo describes his own mission as retrieving koseki that are being destroyed year after year, once a register is disposed of, that part of the record is gone.
Paper records can be lost
Some registers have already been destroyed by war, fire, earthquake and flood over the past century. Retrieving certified copies now places your family's record safely in your own hands.
Rules and systems change
Access rules, formats and the family-register system itself continue to evolve. Records that are retrievable under today's procedures may be harder to obtain under tomorrow's.
Interest in koseki research has also surged, some well-known overseas programs have paused new requests under the demand. Yuzo works with clients directly from Osaka and is taking new enquiries now.
You do not need to know everything before you enquire
Koseki research often starts with incomplete family information. Send Yuzo whatever you already know and he can assess the most practical starting point.
Old family documents can be especially useful because Japanese names, former addresses, municipalities and registered domiciles may help identify where relevant records are held.
Helpful information may include
- Your ancestor's Japanese name, if known
- Approximate year or date of birth
- Known town, city or prefecture in Japan
- Your relationship to the person
- Old passports or immigration documents
- Family letters, photographs or certificates
- Japanese addresses or handwritten notes
How Yuzo helps
Yuzo handles the process from Japan while you remain overseas: assessing what you know, identifying the likely municipal office, preparing the necessary authorisation where required, retrieving eligible records and translating the documents according to the agreed scope.
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Tell Yuzo what you know
Send the names, family information and documents you already have.
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Receive a quotation
Yuzo assesses the likely retrieval path and provides a written quotation before work begins.
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Sign a Power of Attorney
Where a Power of Attorney is required, Yuzo prepares the form for you to sign so he can act on your behalf with the relevant municipal office.
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Retrieval in Japan
Yuzo requests the eligible family-register records from the relevant municipality or municipalities in Japan.
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Translation and delivery
Retrieved records are translated and delivered according to the agreed scope and quotation.
What you receive
The exact deliverables are confirmed in Yuzo's quotation and depend on the records available and the scope of the work.
Japanese family-register records
Copies obtained from the relevant municipal authority as part of the agreed retrieval work.
English translation
English translation of the retrieved Japanese records prepared by EAI according to the agreed scope, with explanatory notes where the old formats, era dates and place names need context to be understood. See a sample koseki translation (PDF).
Agreed delivery
Digital and/or physical delivery can be confirmed as part of the quotation and engagement.
Pricing
Yuzo agrees the scope and provides a written quotation before commencing work.
Koseki retrieval
Depends on the records, municipalities and retrieval work involved.
Koseki translation
Translation pricing shown for koseki-related documents.
Power of Attorney / administration
Quoted according to the authorisation and administrative work required.
Finding & escorting to your living relatives in Japan
Depends on the time and work involved.
The total quotation may vary depending on the number and location of records, the complexity of the family line and the work required to establish the retrieval path.
About Yuzo Ochiai
Yuzo Ochiai has worked as a translator and interpreter for fifty years. A native Japanese speaker, he lived in the United States from 1969 to 1976 and holds a Bachelor of Arts in Music from the California Institute of the Arts (1976).
On returning to Japan he founded EAI, the English & Art Institute, in Ibaraki City, Osaka, between Osaka and Kyoto. Alongside teaching, he has worked ever since as an interpreter and translator for firms and private clients, with a particular focus on genealogy and family-record work for clients overseas.
Yuzo handles enquiries personally, agrees the scope and quotation before starting, and remains the client's direct point of contact throughout the work.
- Based in Ibaraki City, Osaka, Japan
- Languages Japanese (native), English (US-educated)
- Experience 50 years in translation and interpreting
- Education California Institute of the Arts, BA in Music (1976)
- Company EAI, English & Art Institute, Osaka (est. 1977)
- Professional Listed member, Association of Professional Genealogists (APG)
- Pricing Written quotation before any work begins
Specialists on both sides of the Pacific
Koseki research often needs work in two places at once, records and offices in Japan, and family history context overseas. MedicTranslate partners with a specialist on each side.
Linda Harms Okazaki · Linda's Orchard
Professional genealogist specialising in Japanese American heritage. Past president of the California Genealogical Society, consultant to Densho and Ancestry's ProGenealogists, and columnist on finding Nikkei roots. Linda helps US-based families build the research picture around the records Yuzo retrieves. APG profile
Yuzo Ochiai · EAI
Retrieves the registers from municipal offices, delivers English translations with explanatory notes that make the old records easier to grasp, and searches for living relatives when requested. He once took a client from the USA to Okinawa to meet ten relatives across both his paternal and maternal sides, twenty people in all. Listed member of the Association of Professional Genealogists. APG profile
Trusted by families tracing their roots
Yuzo has published client stories on the EAI website spanning more than a decade of genealogy and family-reunion work. A few highlights, in brief.
Genealogy specialists
Linda Harms Okazaki, past president of the California Genealogical Society, consultant to Densho and Ancestry's ProGenealogists, and columnist on Nikkei family roots, has worked with Yuzo since 2017 and praises his accuracy in genealogy translation, noting he keeps interpretation clearly separate from the document's contents.
Family reunions
In 2024 Yuzo coordinated an Osaka reunion for the McCoy family, bridging correspondence for months in advance with relatives one member had not seen in 55 years, and interpreting on the day.
Ancestral hometown visits
Families from the US, Australia, Germany, and Peru describe Yuzo locating relatives from fragmentary addresses, accompanying them to ancestral hometowns, and easing first meetings across the language gap.
Full client stories are published on the EAI website.
Frequently asked questions
An independent MedicTranslate partner
Koseki retrieval and translation services described on this page are provided directly by EAI / Yuzo Ochiai. Genealogy research services in the United States are provided directly by Linda Harms Okazaki (Linda's Orchard). Each partner determines the scope, quotation and delivery arrangements for their own services. MedicTranslate may assist with introduction or coordination where a customer also requires MedicTranslate services.
Ready to investigate your family's Japanese records?
Send Yuzo the information you already have. He can review the enquiry, identify the likely next step and provide a quotation before work begins.
The records that can ultimately be obtained depend on the family, municipality, surviving records, the information available and the applicable requirements for the request. No particular historical record or outcome can be guaranteed.
Contact Yuzo
- Email: inquiry-eai@e-a-i.net
- Mobile: +81-90-3973-1232
- Location: Ibaraki City, Osaka, Japan
- Website: EAI English website
- 日本語: EAI 日本語サイト