The yen hit fresh 17-month highs against the dollar on Thursday.
The drop in the dollar came after the latest Fed minutes pointed to a cautious approach on rate hikes.
The dollar fell 1.2% to 108.47 yen, its weakest against its Japanese counterpart since October 2014.
The yen’s surge led to more warnings of action from Japanese officials.
A senior Japanese finance ministry official said it would take steps in the market as needed.
Bank of Japan Governor Haruhiko Kuroda also repeated that the central bank would ease policy further if needed.