The 14 percent plunge in the yen since mid-year has about run its course, according to the former Finance Ministry official known as "Mr. Yen."

Eisuke Sakakibara, who got his nickname in the 1990s for his influence over the exchange rate, said the yen is unlikely to match its low of 124.14 per dollar on the eve of the financial crisis in June 2007.

It touched a seven-year low of almost 119 to the dollar last week after more than a year and a half of unprecedented monetary easing by the Bank of Japan.