Adam posted on the drop in USD/JPY, and then its roar back:

In Japan it’s the Ministry of Finance that directs the Bank of Japan to intervene in the FX market.

An official at the MoF has been asked if the episode was intervention. The reply was along the lines of:

• there will be cases where we will disclose, or not disclose, whether we intervened

Nothing burger, but in defence of the official, if it was intervention the MoF had its *** handed to them. And admitting to such a failure would not be helpful to the MoF.

Adam’s chart at the time shows the move: