Japan could cure their high Yen/low Dollar problem by dumping their US treasury holdings. They may be second only to China as foreign holders of US debt, and China has been unloading theirs. That would overwhelm Fed's ability to keep rates low through buying treasuries. The Fed knows they would throw the World economy into chaos if they attempted to print enough new money to buy the bonds sold by them. Moreover, if Japan started selling that would cause others to sell and there would be a run on US debt. Instead, the Fed would grudgingly raise rates to protect the Dollar. Japan's currency cross problem would be solved.