JPY intervention may be against EUR, BNY Mellon says, as well as against USD, whenever it comes. "Forewarned is forearmed," the bank says, although with Japanese currency strength fading this week that intervention risk hardly feels imminent.

BNY Mellon says the MOF is unlikely to return to a campaign of purely stealth intervention since this tactic has proved ineffective in the past, but adds a mix of shock-and-awe tactics followed by more stealth-like intervention is possible.

As such "we must also assume that the peak of JPY weakness may not be reached until several days after the first strike," BNY Mellon says.