Japan Pension and who has agreements where you can transfer credits for the basic state pension.
According to http://www.nenkin.go.jp/n/www/english/detail.jsp?id=34 the list of countries with such agreements with Japan are Germany, United Kingdom, Korea, United States, Belgium, France, Canada, Australia, Netherlands, Czech Republic, Spain, Ireland, Brazil, Switzerland.
The Japanese National Pension System, which is the Japanese equivalent of Social Security. In order to get money from that you need to have paid for at least 25 years (might get decreased to 20 for foreigners, but not yet). Also, the amount you get is whopping 65,541 yen per month for 40 years of contributions. Less for under 40 years …
References to numbers are from here:
http://www.nenkin.go.jp/n/www/share/pdf/existing/english/pdf/1.pdf
(1) Old-age Basic Pension
If you have paid the National Pension contributions for at least 25 years and satisfy the conditions, the following amount is paid when you become 65 years old. *1
★Benefit amount = Y786,500 (annual amount in Fiscal Year 2012 for those who have paid contributions for 40 years) that is only 65,542 per month!
When you go for the lump-sum payment, you are giving up any benefits, including credit under the agreement. Unless they make a mistake, they will simply delete you from their system after you refund request is processed. This is based on the first bullet under “Important Notes” on page 5 of:
http://www.nenkin.go.jp/n/open_imgs/service/0000005247.pdf
So depending on the system you are ending up in the credit may be more than the money you get back but that is assuming the system you end up in survives.
From the Japan Pension service website:
http://www.nenkin.go.jp/n/www/english/detail.jsp?id=39
An article from the US Social Security Administration:
http://www.ssa.gov/policy/docs/ssb/v67n3/v67n3p89.html
