USD/JPY fell by up to 0.5% after the BOJ announced "tapering" to its JGB purchases earlier today
The BOJ earlier announced that they would trim purchases of 10 to 25-year debt to ¥190 billion (compared with the ¥200 billion previously), and also scaled back on purchases of 25-years+ bonds to ¥80 billion (compared to the ¥90 billion previously).
While Kuroda has in the last month came out to talk a lot about the yield curve control (YCC) being the main toolkit of the BOJ - and it has been since its implementation in 2016, markets are still nervous in reacting to this sort of news.
The "tapering" today doesn't offer any new immediate policy implications, but it is taken as somewhat of a signal that the BOJ is moving towards normalisation of monetary policy by the market.
The BOJ still has a long way to go before removing accommodation. Inflation is still underwhelming, and it will take quite some time before the BOJ even considers to start thinking about a policy change.
If this was the market reacting to a "taper" which does nothing, imagine the reaction when the BOJ actually starts changing their YCC policy.