You can't travel to Jeju Island again

Generally speaking, after entering the country illegally or returning to China illegally, you will permanently lose the right to re-enter the country.

Because the illegal certificate "illegal" will be left on the passport, this is very unfavorable for entering other countries.

So you can't travel to Jeju Island again. Jeju Island also belongs to Korean territory. Even if you are visa-free, you still need to show your passport when you enter the country. At this time, you will be stopped and repatriated.