They were able to warn everyone in real-time when North Korea launched those missiles. A quick search turned up this article that the J-Alert system is not perf

They were able to warn everyone in real-time when North Korea launched those missiles. A quick search turned up this article that the J-Alert system is not perfect: https://www.japantimes.co.jp/news/2018/04/10/national/japans-vaunted-quake-missile-alert-system-runs-limits/#.Xam_uOhKhaQ https://www.japantimes.co.jp/news/2018/04/10/national/japans...