Jeju Island - Visa-free entry via direct flight but indirect exit allowed?

Question

I am an Indian citizen. My travel plan is as follows:
Delhi->Singapore>Pudong->Jeju.
The return route is:
Jeju->Incheon Intl Airport->Singapore->Delhi

So, I am not stopping over in mainland Korea during entry to Jeju but doing so during the return. Is it possible to do so?

Also, the booking websites (makemystip, goibibo) mention that I need a transit visa for Delhi-Jeju. Why is it so?

Answer 1

You cannot set foot in Korea, outside Jeju, without a visa. Jeju<>Incheon is a domestic flight, and you can't board that flight without a visa.

You need to change your itinerary to avoid passing through Incheon (or any other city in Korea).