I moved to Japan around 2 years ago and I did not know about that until right now. I'm not surprised though because there has been news about an incident that happened a couple of months ago (As well as a YouTube video)where the Japanese guy in the aircraft spotted the Korean boats and towards the end they see that the fc radar is pointed towards Japan and wouldn't respond when they asked what their purpose was. They were caught red handed and they tried to be sneaky about it. To this day, they deny it happened even though there's evidence.
This is the video: https://youtu.be/s93-l68D3Eo
The middle towards the end is were they were able to spot things.
Knowing this, it doesn't surprise me that Korea launched projectiles, China and korean have been low key asking for war with Japan since the Big Earthquake back in 2012 I believe, possibly even before but those are other big issues.
