There's no stopping the Japanese yen today as it seems like those who were short i.e. long USD/JPY over the last few months, are all jumping ship. I find it hard to fathom that Ueda's remarks earlier today can be that big of a catalyst. However, it is perhaps a trigger point coupled with a break in the technicals in USD/JPY as well as catching up to the big plunge in Treasury yields recently:
We've known for about a month or two now that the BOJ has kicked the can down the road to March to April next year on any real hints of a policy shift. They kept alluding to the spring wage negotiations next year and that is still the same rhetoric that Ueda has mentioned today, even if he did open up more communication on exiting the current ultra easy policy.
I'd say that this is more of the fact that yen shorts have given up hope for a return to the trend that has prevailed for the majority of this year. The trade in the yen now is whether or not the BOJ will follow through after the wages outcome and traders are convinced that they very well might.
As such, this looks to be a case of yen shorts bailing and that is exacerbating the fall in yen pairs today. The technical break from the end of last week (USD/JPY falling below the 100-day moving average) and the heavy decline in Treasury yields were already key factors but it would seem now, the BOJ is giving traders a reason to go running.