You can't get a flight straight to busan all international flights go to Incheon and transfer to the next destination. Your best be is to book a flight from Shanghai to Seoul, then straight to Jeju Island. But your really not missing anything. If your gonna spend all that monet on a flight go to Bali, Indonesia by far the best place to visit for the island life trust me you won't be sorry.

Fly. You can fly from Shanghai to either Incheon or Busan. From there, you can get a flight to Jeju Do.

I know that you can take a ferry from Shanghai to Gunsan, and I know that you can take a ferry to Jeju-do, but I don't know if there's a direct ferry from Shanghai to Jeju. That would be the cheapest, if not fastest way.

flight or its posible via ferry