The Japanese government warning protocol on missile tests could be helpful to yen traders.
For example, in Hokkaido this morning as the North Korean missile test was incoming, residents received two text message missile alerts , alongside air raid sirens sounding. Quick on the trigger yen buyers could well use this information to enter trades.
I suppose it depends on how motivated you are but there is an opportunity there for keen forex traders!
(ps. I apologise in advance for making such a mercenary suggestion :-D )