Bank of America Global Research of the this week's wave of MoF's yen intervention.

"We think this attempt could possibly be more effective than previous episodes earlier in the year. 

First, the move comes on the heels of aforementioned USD weakness, which is a notable change from conditions where USDJPY reached fresh highs on broad USD strength. Thus, they are in a place now to blow with- rather than against-the wind.

Second, the yen has clearly lagged the recent appreciation of the KRW (on equity hedging flows). This leaves room for catch-up for similar reasons, should Japan specific policy concerns moderate," BofA notes.

"Third, broader yen sentiment remains subdued, and the market is still positioned short, opening the door for a position-squeeze.

Finally, should the move extend further, we think Japanese exporters could become incentivized to sell USDJPY, should the pair approach the ¥155 level (~¥159 at the time of writing). This could provide fresh downside pressure, or serve to offset potential buying pressure," BofA adds.