Tracing Your Japanese Family Roots: Koseki Records, Letters and Finding Relatives

If you have Japanese ancestors, you can often trace your family back several generations through Japan’s family register system, the koseki (戸籍), as long as you can prove you are a direct descendant and know which municipality held the record. The process usually means gathering your family documents, finding the ancestral “registered domicile” (本籍), and writing to the city, town or village office in Japanese to request copies. Older registers can be handwritten and hard to read, and some very old ones no longer exist. Help with Japanese letters, reading old documents and calls with offices or relatives makes the search much easier. Here’s how it works.

Start with what your family already has

Before contacting Japan, collect everything you can find at home:

Names in Japanese characters, not just in romaji. The same romanised name can be written many ways.
Birth, marriage and death dates and places.
Old letters, postcards, photos with writing on the back, and family altar items such as memorial tablets.
Immigration, naturalisation or travel documents, which may record a hometown in Japan.
Family stories about the village or prefecture your family came from.

How the koseki works

A koseki records a family unit: births, marriages, adoptions, divorces and deaths. It is held by the municipality of the family’s registered domicile, which is not necessarily where anyone lived. When people married or the system was reformed, new registers were made and old ones closed. Closed registers are called 除籍 (joseki) or 改製原戸籍 (kaisei genkoseki), and these older records are what genealogists look for.

Who can request copies

Koseki are not public records. Generally, only the people listed, their spouses and their direct ascendants and descendants can request copies, so a great-grandchild can usually request a great-grandparent’s register by proving each link in the chain. That proof is typically a set of documents, such as birth certificates from your own country, translated into Japanese. Rules and fees can change, so check with the municipal office before you send anything.

Requesting a koseki from abroad

Identify the municipality of the registered domicile. Place names may have changed after mergers, so check the current name.
Prepare a request letter in Japanese explaining who you are, whose record you want, why and how you are related.
Include proof of relationship and identity, with Japanese translations.
Arrange payment. Many offices accept postal money orders (定額小為替), which are hard to buy outside Japan, so ask what they accept from abroad or ask a contact in Japan to help.
Include a return envelope or ask how they will send the documents.

Reading what you get back

Older registers may be handwritten in cursive, use old kanji forms and era dates such as Meiji, Taishō and early Shōwa. Converting era years to Western years is easy once you know the starting year of each era, but the handwriting can challenge even native speakers. Ask for help reading it rather than relying on a phone app.

Finding living relatives

A register can lead you to a family home, a temple that holds family graves, or living relatives. Contacting them is sensitive: write a polite letter first, explain who you are and include photos and a family tree. Many families are delighted, but give people time to reply. Our guide to translating letters to and from Japanese has tips on tone.

What we can and can’t do

Hanabuddies can translate your documents and request letters for reference and help you read what comes back, but we don’t provide certified or sworn translation. If an office asks for a certified translation, ask exactly what they accept. We also tell you honestly if a handwritten record is beyond what we can read reliably. For documents needed for official purposes, see our guide to translating Japanese documents.

How Hanabuddies can help

We help families with Japanese roots write request letters in Japanese, translate letters, photos and records for reference, and interpret live for calls with municipal offices, temples and newly found relatives, over video or in person if you travel to meet them (you cover travel expenses). Tell us what you already know about your family and what you’d like to find out.