This news was out earlier, but in case you missed it (like me), here it is: South Korean intelligence agencies expect North Korea to launch a missile test “imminently”. Depending how close the tests come to Japan, often these exercise prompt some short-term JPY weakness.
The JPY is anything but weak at the moment as US equities trade in the red. USD/JPY is now at 100.80 after failing to absorb offers at 101.50 early in the session.