Seoul or Busan first? Start with your final night, not a north-to-south map

Choose the first and final city from your actual flights, then place the Seoul–Busan KTX between complete stays. The route looks simple on a map; luggage, check-in and a departure-day train decide whether it works.

Set the airport nights before the city order

Write down where you land, where you fly home from and how late you arrive. If immigration and luggage will push a Seoul arrival late, use Seoul for the first night and transfer the next day rather than adding another uncertain connection. A late Busan arrival needs the same buffer. With a Seoul return flight, you can still visit Busan first, provided you return to Seoul before departure day.

Give the KTX a day with room around it

Check out, move luggage, take the train and reach the second hotel before adding more than one local plan. Avoid placing a fixed show, early flight or long-distance excursion right beside the KTX day. Search the actual travel date and station pair on the KORAIL English booking page; do not base the transfer on a timetable from another date.

Choose an order that protects the days you care about

Seoul first can work when arrival is straightforward, Busan is the departure city, or you prefer to finish with Seoul shopping and dining. Busan first can work when you can connect there after landing and want Seoul near a Seoul departure. If your arrival is very late, keep the first night in the landing city; if your return flight is early, do not put the Busan-to-Seoul train on departure day.

For a trip of around five nights, a two-night/three-night split is one possible starting point, not a rule. Give each city enough nights for its fixed activities and transfer burden. If both cities need equal time, compare the last hotel move and the location of your first activity rather than forcing a 50/50 split.

Once the order is set, choose the hotel areas separately. In Seoul, use the base guide and one-base or split-stay comparison; in Busan, check whether Seomyeon, Haeundae, Nampo or Gwangalli matches the days you have. The Busan night-count guide helps test whether the stay is long enough.

When the flight times are confirmed but the KTX is not, hold a cancellable room at each end and finalize the city order after checking the train and hotel check-in conditions.