For six months the Japanese jawboning has seen investors front-running the BoJ, selling JPY and buying whatever risk-asset is the most correlated that day - whether it is the Nikkei 225 or the S&P 500. However, now that words have been replaced by actions, it appears that someone (cough Japanese institutions cough) has decided the 13.4-sigma swing in JGBs last night is just too much and have rotated to US Treasuries. The selling of JPY and buying of EUR (to fund peripheral bond buying) and USD (to fund Treasury buying) is very clear. That means, implicitly, that every ramp higher in JPY (weaker JPY) is simply more bond-buying - which leaves the algos directionless.
If you were a risk-manager, what would you do? And as far as all those VaR risk models - oops!!
It seems the 'sellers' of those JGBs have found a new place to put that capital to work (and in a non-devaluing currency)...