Guk is actually a derogatory term for Koreans but only in the USA. All Koreans are Hanguks, Americans are MeeGuks foreigners are Wayguks. During the Korean war American Soldiers kept hearing Meeguk,wayguk, hanguk, so the shortened the term to Guk to describe the Koreans.

I figured if you were going to use a racial slur improperly you might as well learn what it means. You should have used JAP in your title