What a koseki is
The koseki (戸籍) is Japan’s official family register. It is kept by local municipal offices and records legally recognized family relationships and civil-status events for a family unit, including births, marriages, divorces, adoptions and deaths. The modern system dates to 1872, so it is usually the most important official source for Japanese family history, and often the best place to begin.
Unlike a birth certificate, which describes one event, a koseki groups the members of a household on one document. That makes it useful for finding parents, siblings, spouses and sometimes the earlier register that an entry came from. For the birth-specific side of this, see Japanese birth records.
Key terms to know
- Honseki (本籍): the family’s registered domicile. It determines which municipal office holds the register. It is not necessarily where the family lived.
- Koseki tōhon (戸籍謄本): a certified copy of the whole register, listing every member.
- Koseki shōhon (戸籍抄本): a certified extract covering one or some members.
- Genkō koseki and jōseki: current registers versus closed ones, usually closed after all members have died, married out or moved their registration.
- Kaisei genkoseki (改製原戸籍): an older form of register kept after the system was revised. These often lead back a generation or more.
Find the honseki and the kanji first
Records in Japan are held locally, not in one national archive. To request a register you generally need two things: the honseki and the correct kanji for the family name. Romanized spellings are not enough, since many different kanji can be read the same way.
Good places to look for them:
- Old passports, visas, immigration or naturalization papers
- Marriage and death records from the country where the family settled
- Family letters, postcards, and photographs with writing on the back
- Funeral programs, grave markers or temple records
- Relatives who still read Japanese
Who can request a koseki
Japan restricts access to family registers for privacy reasons. As a general rule, the person named in the register and close direct-line relatives, such as parents, grandparents, children and grandchildren, can request copies, and you may be asked to document the relationship. Rules and procedures can change and can differ by office, so check with the municipal office concerned, or ask a Japanese consulate, before sending anything. Some researchers use a professional or translator in Japan to handle requests, which usually involves written authorization from you.
Other Japanese record types
- Kakochō (過去帳): Buddhist temple death registers. They may list posthumous names, birth names and death dates, and can sometimes reach back further than the koseki.
- Jūminhyō (住民票): residency records, which show where a person lived. Access is also limited.
- Genealogies and local histories: some families kept their own lineage records. FamilySearch lists Japanese genealogy collections in its wiki.
- Land records and cadastral maps: useful for locating an ancestral home.
Japanese American and overseas records
If your ancestors emigrated, records outside Japan may carry the details you need to ask for a koseki: ship passenger lists, naturalization or alien registration files, World War II-era records, draft registration, and census entries. Densho and FamilySearch both publish guidance for Japanese American research, although services that handle koseki requests have at times paused for new clients, so check current availability.
Reading the records
Registers are written in Japanese, older ones in handwritten script, and dates use era names such as Meiji, Taishō, Shōwa, Heisei and Reiwa rather than Western years. Convert era dates carefully, and have the key entries translated or checked by a fluent reader. Machine translation may help with a first pass but should be verified.
Finding a family crest
The Japanese family crest is called a kamon (家紋). A crest is not fixed to a surname, and families sometimes used more than one. Useful clues include crests on a family grave, kimono, lanterns or old household items, and the family’s temple. Crest reference books can help you compare designs, but a match alone is not proof of lineage.
Who were the Japanese ancestors?
Most people in Japan today descend from long-settled populations of the archipelago, and scholars generally describe the population as having mixed origins over a long period. Ancestry tests may report Japanese or East Asian results, but they say little about a specific family line. See DNA testing for Asian ancestry and choosing an Asian ancestry test for what to expect. Records are the way to identify named ancestors.
A practical research order
- Gather everything from relatives and from records in your own country.
- Confirm the Japanese name in kanji and identify the honseki.
- Identify the municipal office for that honseki, noting that municipal mergers may have changed names.
- Request the current register, then look for earlier registers it refers to.
- Add temple records and local sources for earlier generations.
- Record each source and translation as you go.
Limits to expect
- Closed registers are kept for a limited period, and some older registers have been lost to war, fire and disasters, so gaps happen.
- Privacy rules may block access to people outside your direct line.
- Fees, forms and processing times vary by office.
- Language is often the biggest obstacle. Budget time for translation.
Researchers working on neighboring countries may also find our guide to Korean ancestry search useful, since both rely on locally held family records and name characters.