JPY weakened after the (most-telegraphed ever?) Bank of Japan tightening on Tuesday:
I've seen notes now warning that the Bank of Japan may have to intervene. UBS, for example, says that now the tightening is out of the way, and there are no further moves expected on the foreseeable horizon, traders may very well feel emboldened to take USD/JPY higher. Yen is exposed to a further weakening, and traders would thus do well to be warty of intervention to keep the yen from sliding too far.
At the very least I expect verbal 'jawboning'. Japan's Ministry of Finance did have success with this late last year:
I wonder if it'll be as easy this time though? I don't think so.