Take an Airport Limousine Bus #6015 at 5B or 12A at the bus stop on the 1st floor at Incheon airport.
Get off at Sejong hotel. You can find a crosswalk after a couple of minutes walk towards Myeong Dong station. Cross the street at the crosswalk. Take a right turn and walk down 30~35meters. Then you should see the Pacific Hotel on your left side. Take a left way in front of Pacific Hotel. Keep going on along the left way beside Pacific Hotel until you find MINI STOP convenience store. Walk along the right way from MINI STOP store. You can find Guesthouse The Hill along the way.