North Korea flashed a Hwasong-12 ballistic missile at a maximum altitude of 550 km, flew more than 2,700 km and crossed the Japanese sky before dropping into the North Pacific Ocean. Experts say there are many reasons for Pyongyang's use of the trajectory, which includes geographic and historical factors.
I think the message is pretty simple here, the North Koreans wants the Japanese to know that they are capable of hitting them whenever they want, Japan and South Korea should have an anti missile shield in place in order to thwart any future attacks by the North Koreans because this is a direct threat.