Often people say that the best way to know more about your own country is to live somewhere else.  This is true in the sense that nobody is likely to think that their own country is particularly unique as the way things are done locally is the "normal way" as far as they know.

The family register system (Juminhyo, 住民票) is another place where most Japanese people wouldn't know that things are done overseas, while foreigners wouldn't likely know much about Japan's system either.

Actually, Japan's system is no so unusual in that many Asian countries follow a similar system.  We'll compare the the family register system used in Japan to the various systems used in the United States. (The systems used in many western countries are similar to the U.S.)

In Japan, each family has a single Family Register, which contains all members.  Basically speaking, children are included on the parent's family register until and unless the children create their own family register.  When one marries, they either join their spouse's Family Register, or their spouse joins theirs.  (Traditionally the wife joins the husband's family register, however the reverse case is also quite common).  Everyone on the family register by definition has the same family name.

The family register is maintained by the local government, and is considered mandatory.  Whenever a Japanese resident moves, they are to report to the local municipal office and give their new address, etc.

Prior to 2012, foreign nationals residing in Japan were recorded in a separate system, however these people have now been merged into the Juminhyo system.  As such, the Juminhyo now contains additional fields for data such as nationality.

The data in the Family Register is maintained by the local government and [usually] shared between municipalities by a system called JUKI net.  There is no "Original" copy of your Family record, the government office simply prints out a copy whenever one is needed.  (Typically only people on the Family Register can request a copy directly from the government).  The copies typically have the issue date printed on them.  While there is no official "Expiration Date", however depending on where you use the document, the receiver will usually not accept documents older than 90 days.

The interesting thing about the Japanese Family Register is that one single document (Which is usually a single page) can be used for many purposes.

You may be asked for a copy of your family register if you open a bank account, buy property, get married, sign up for contracts, etc.

The family register is typically only one page, perhaps two for a larger family - but it is deceptively simple.  The Juminhyo proves who lives where, who is part of the family, whether or not one is married, etc.

Contrast this to the US where instead of a single family register, there is a myriad of documents maintained by different governments.  

In order to obtain the same information in a single family record, you would potentially have to apply to a large number of places and pay multiple fees.  You may or may not be entitles to the information depending on the law in the particular area, and you might have to wait processing times and mail.   Worse yet, it isn't always clear where to get each document in the first place.  

Think about this example:  If you are single, have two siblings and your parents are divorced and one is deceased.  In order to get all of the information about your family, you would need:

a. 4 Birth certificates

b. Marriage certificate

c. Divorce certificate

d. Death certificate

That's 7 documents, potentially from different counties and states, or even countries! (What if one of your parents was born overseas, etc.?)

Some localities won't produce marriage or divorce certificates of the parents for children at all.

If you don't know where f.e. a divorce happened, you won't even know where to apply.

If your family is spread out, has moved a lot, is in any other way complicated, or if you are missing information, it could take you months to collect all of this information - or you may not be able to at all.  

It's also very difficult to prove that you are not something in the U.S.  For example, how do you prove that you are not married or have no children?

On the other hand, you can visit your local city hall and print out a copy of your family register in person for about $5 USD.  The main inconvenience is that you have to go during business hours.  Even that issue has been solved to a certain extent, as many municipalities now offer ATM style machines where you can insert a card, enter a password, and receive a copy of your family register 24 hours per day.  (Depending on the municipality, you may also be able to print out copies of your family register at convenience stores as well!)

Though Japan is often seen as a behind-the-times paperwork loving country, one has to admit that the Family Register system is actually convenient compared with the byzantine system used in the West.

Note that there are actually two types of family register in Japan:

1. The Jyuminhyo, which is maintained by the local governments and discussed above.  The Juminhyo is used to store addresses and other current residency information.  In common usage, it is translated into English as "family register", however.  Since 2012, the Juminhyo is maintained for all residents of Japan, foreign or not.

2. The Koseki, which is also known as the "Family Registry", is maintained by the government office closest to the person's registered "Honseki".  ("Honseki" is meant to be the place of "place of roots", however it can technically be changed to any location at any time).  The Koseki is maintained only for Japanese citizens.  Most of what is mentioned above about the Juminhyo is also true of the Koseki.  For example, the Koseki contains information about birth, death, etc. - but the Koseki is a more formal record and contains historical information instead of just present data.  Much like the Juminhyo, the Koseki system is also common in East Asia, and is used in countries such as South Korea, Taiwan, China, etc.