What Is a Koseki? Japan’s Family Register Explained

A koseki (戸籍) is Japan’s official family register. It records births, marriages, deaths, and family relationships and is the primary document used in Japanese genealogy and ancestry research.

Unlike many Western civil records, the koseki is organized by household rather than by individual certificates alone. For Japanese Americans tracing family history, obtaining and translating koseki records often reveals multiple generations of ancestors in Japan.

At Discover Japan Roots, we help you identify where to request records, retrieve them when possible, and translate them into clear English so you can understand your family’s story.