I've been to Seoul and it is a nice place to punt, but backpage independents is NOT the way to go. Most of them are bait and switch, run by agencies, or you are going to see some old aunties.
Better stick with well-reviewed girls, and a handful of agencies are OK too. Even the agency girls don't have real pictures, so buyer beware! My best experience was with a visiting Thai girl named Tina Yang. Not sure if she is still in Seoul, as she alternates between Korea and Thailand. See my review of her in one of the sections here (maybe newbie section). Best of luck!