At some point, we will get the headlines hitting the wires that the BOJ is buying USD/JPY.
We may also get headlines that the Fed, the ECB and BOE are buying USD/JPY as well., depending on the time of day. That does not necessarily mean that coordinated intervention is underway.
Often central banks will act “as agent” for other central banks, intervening in their local markets and then handing over the net position to, in this case, the BOJ.
Coordinated intervention means that each central bank acts in coordinated fashion for there own accounts, showing the market that each central bank has “skin in the game”, giving the action greater credibility.
The first hurdle the Japanese will want to overcome is 79.75/80.00. Beyond that is the 81.75 area, the support line broken decisively earlier this week.