A rumor of The BoJ doing something moar (helping banks with NIRP loans) was the apparent catalyst for today's epic USDJPY spike, but the kindling was a record position among speculative futures traders that USDJPY would continue to fall.
Today's 250 pips plunge in Yen relative the dollar is the largest since Oct/Nov 2014 when The Fed ended QE3 and BoJ stepped in with QQE2 (or 22).
For now, however, the machines have failed to get inspiration for stock buying euphoria from this usually positive carry pump...
It seems Central Bank omnipotence is really starting to ebb - especially The BoJ's.