The nearest airport is in Seoul (ICN-Incheon Intl.), located 25.5 mi (41 km) from the city centre. If you can't find a flight that's convenient for your trip, you might consider flying into Seoul (GMP-Gimpo Intl.), which is 5.6 mi (9.1 km) away.
Catch a ride on the metro at Dangsan Station for ease of access to the rest of the city.