The nearest airport is in Seoul (ICN-Incheon Intl.), located 24.9 mi (40.1 km) from the city centre. If you can't find a flight that works for your travel itinerary, you could book a flight to Seoul (GMP-Gimpo Intl.), which is 4.8 mi (7.7 km) away.
Catch a ride on the metro at Seonyudo Station for ease of access to the rest of the city.