Japan's holdings of foreign assets a fiscal backstop

Japan Retains Status as Biggest Creditor Nation - WSJ.com

"TOKYO—Japan retained its title as the world's biggest creditor nation in 2011, as the government's currency-market interventions and companies' overseas mergers and acquisitions helped boost the value of the country's foreign-investment holdings.
Japan's net foreign assets—the difference between its holdings of overseas assets, such as currencies and U.S. Treasurys, and its liabilities, such as Japanese government debt held by foreigners—stood at ¥253.01 trillion ($3.19 trillion) at the end of 2011, data from the Ministry of Finance showed Tuesday."

Of course, the flow of funds into Japan from this asset base tends to strengthen the yen.