Hmmm
Quote
Days after Hawaii alert gaffe, Japan issues false alarm about a missile launch
Link here - https://www.yahoo.com/news/now-japanese-tv-issues-false-alarm-missile-launch-104605205.html

Quote
Japanese public broadcaster NHK issued a false alarm about a North Korean missile launch on Tuesday, just days after a similar gaffe caused panic in Hawaii, but it managed to correct the error within minutes.

It was not immediately clear what triggered the mistake.
I'm of the opinion, some one (or group) has hacked the warning system. NK?? playing games possibly, or another group for whatever reason.