is a family register. Japanese law requires all households (ie
) to report births, deaths, marriages, divorces, and criminal convictions to their local authority
, which compiles the information into a detailed family tree
that encompasses everyone within their jurisdiction. If such events are not recorded in the koseki
, they are not acknowledged by the Japanese government
, and can be subject to fines.
While similar systems have been employed in Japan since ancient times, the modern koseki, encompassing all of Japan's citizenry, appeared in the late 1800's, immediately following the Meiji Restoration. This was the first time in history that all Japanese people were required to have family names as well as given names. Records were originally kept in lengthy paper volumes, but were translated to digital format in 2002 and are now kept entirely by computer.
The koseki fills the role that birth certificates, death certificates, marriage licenses, and the census play in other countries, all in one package. Because they often contain sensitive information, such as adoption records, they are usually held in strict privacy by the government, and are usually only shown to family members, the police, and employers (who sometimes use koseki data to weed out burakumin, Koreans, and other undesirable employees).
A typical koseki has one page for the household's parents and their first two children: additional children are recorded on additional pages. Any changes to this information have to be sealed by an official registrar.
This situation can pose some problems for gaijin who become involved with Japanese nationals. Because they aren't recorded in the national koseki rolls, any children they have with a Japanese person may appear to be illegitimate. The only way around this is to expressly request to be added to the Japanese spouse's personal information section.
If you need somebody's koseki (for genealogy research or whatever), you can submit a request for a copy. All koseki records from before 1886 have been destroyed or closed, and some municipalities have disposed of koseki more than 80 years old, but in most cases it isn't too hard to get the records.
You can see a modern printed koseki at http://www.debito.org/ayakoseki.jpg, and a Taisho era handwritten one at http://www.geocities.com/SiliconValley/Garage/4464/KosekiPage1.html.