Norinchukin Bank, the farm lender with most of its money invested overseas, says it sees little choice but to put additional funds into foreign assets this year even as U.S. debt markets become more volatile.

The bank, which had ¥64.2 trillion ($523 billion) of securities at the end of March, more than doubled net income to a record ¥411.3 billion last fiscal year. A 14 percent drop in the yen versus the greenback boosted interest income from overseas holdings, almost all of which are in bonds or other credit investments, said Shinichi Saitoh, a senior managing director at Norinchukin.

"We have no choice but to look for dollar or euro" investments when Japanese government bonds mature or there are new deposit inflows, Saitoh said in an interview at the bank's headquarters in Tokyo last week. "Funds that we have to keep in yen, we will keep with the Bank of Japan."