The nearest airport is in Seoul (ICN-Incheon Intl.), located 25.7 mi (41.4 km) from the city centre. If you can't find a flight that works for your travel itinerary, you might consider flying into Seoul (GMP-Gimpo Intl.), which is 5.3 mi (8.6 km) away.
Catch a ride on the metro at Mangwon Station for ease of access to the rest of the city.