I just arrived in Korea and I'm feeling pretty isolated?

That feeling is really common in the first few months, and there's a big support network once you find it. For meeting people, Meetup and Facebook groups like Seoul Expats or city-specific expat groups host language exchanges, hiking, and social nights, and language-exchange apps plus local sports clubs are popular ways in. Many cities have a Global Center or Foreigner Support Center (the Seoul Global Center and others run by local governments) offering free events, classes, and counseling in multiple languages, and university towns and religious communities are also easy places to find people. Reaching out feels hard when you're low, but joining even one regular weekly activity tends to turn things around faster than anything.