Take a look at this great circle plot. ...
http://gc.kls2.com/cgi-bin/gc?PATH=icn-hik%0D%0A&RANGE=&PATH-COLOR=&PATH-UNITS=mi&SPEED-GROUND=&SPEED-UNITS=kts&RANGE-STYLE=best&RANGE-COLOR=&MAP-STYLE=
Northern Sea of Japan, not southern.
The missile was launched from Incheon International Airport??? I don't think that's in NK.