You do not need a bus tour to get a K-drama feeling in Seoul. Several filming-friendly landmarks sit on ordinary subway routes, so the easiest plan is to choose two or three places you would enjoy even without recognizing a scene.
Start around City Hall with the Seoul Museum of Art (Seosomun Main Building). Visit Seoul lists it among K-drama filming locations, and the historic façade makes the stop worthwhile even when there is no production underway. City Hall Station is a short walk away.
From central Seoul, Gyeongbokgung gives you the palace side of the K-drama image. It is one of the city’s most recognizable historic settings and is easy to combine with Gwanghwamun and Seochon. Check the palace schedule before going; it is normally closed on Tuesdays.
For a completely different mood, finish around Namsan Seoul Tower. Visit Seoul lists the tower among TV-show filming locations, and the real reason to go is the wide city view. Sunset into night works especially well if you want the Seoul skyline rather than a specific drama screenshot.
If you prefer cafés and alleys, Euljiro is another direction. Visit Seoul highlights Hyemindang and Coffee Hanyakbang in its K-drama location coverage, linking the area to Hotel del Luna. The point of a good filming-location trip is not to reproduce a frame exactly; it is to discover a part of Seoul that still works after the fandom moment passes.