The yen's recent weakening may not be as rapid as last year when it lost around 20% of its value relative to the U.S. dollar, but the prospect of it staying longer at current levels is already a cause for alarm for corporate Japan and consumers.

The yen is in the ¥143 zone to the U.S. dollar, far from around ¥130 that major Japanese firms expect the currency pair to average in the current business year to next March. The euro has also hit a 15-year high versus the yen near ¥157.

While Japanese authorities say they are closely monitoring forex developments due to the importance of stable currency moves that reflect economic fundamentals, the yen's recent weakness is largely due to the divergence of monetary policies between Japan and its peers in the United States and Europe.