Landed in Seoul and got eSims from LGU+ at the airport. Did it in person because we wanted local phone numbers because reasons. You have to show a passport for that. Got unlimited dat for 55,000 won (~$60) for 15 days and 20 minutes of outgoing calls for 5,500 won. Setup was so fast and competent. We each did one phone and the whole thing took maybe 5 minutes (after a wait in line of 10-15) Anyway if you need a local Korean number on a trip, I highly recommend this way of getting it.