The commonest mistake on a first two-night trip is trying to cover east and west in one day, because the island looks small on a map.
The numbers settle it: 73 km east to west, and a ring road of over 200 km. Get ambitious and you spend six hours in the car. There is one answer — one east day, one west day.
Day 1 — east, about 3 hours of driving
Collect the car at the airport, then Hamdeok Beach → Manjanggul → Seongsan Ilchulbong.
Manjanggul is a UNESCO lava tube and sits at 11 to 21 degrees inside — you want a layer even in August. Arrive early and you can add Udo, a 15-minute ferry each way from Seongsan.
Day 2 — west, about 3.5 hours of driving
Hallasan's Eoseungsaengak or Saryeoni Forest → Hyeopjae and Geumneung beaches → sunset at Aewol. Day two is the real full day, so spend your energy and your planning here.
Day 3 — the city and the airport
Keep it light around your flight: Dodubong, Iho Tewoo, Dongmun Market is plenty. Put something distant on the last day and you will either miss the flight or see nothing.
Where to stay
Between Seongsan and Pyoseon works well. It keeps day two's westward drive manageable and sits near the end of day one's route. On a two-night trip the hotel's location is half the itinerary.
What this trip leaves out
Two nights does not fit the south. Jungmun and Seogwipo need another day, and with that day the whole order of the loop changes.
Day-by-day routes with driving times between stops are on the WeBring blog.