Korea is a peninsular nation in East Asia.
Real World Background
Korea was divided as a nation after World War II when the country, a Japanese colony, was split into zones of occupation between the United States of America and the Soviet Union. In 1948, two nations emerged from the zones of occupation, the Democratic People's Republic of Korea (North Korea) and the Republic of Korea (South Korea). From 1950-53, a war was fought between the two Koreas which ended in an armistice or ceasefire. The two nations technically remain at war since a peace treaty has not been signed.
The decision to put a gargoyle clan in Korea was because that was one of the places the show was animated. 
- Korea at Wikipedia, the Free Encyclopedia