i know you wrote this a while ago, but i've been out of korea for a while myself. my name is dusty and i live in gyeongsan, a suburb southeast of daegu. there are a couple of good crags i know north of you, one call mu-cheok-san near pohang. the other is mun-su-san, which i think is close to ulsan. both of these places offer amazing sport climbing. mu-cheok is very sharp rock and offers good shade in warmer weather, while mun-su is south-facing and is pretty popular in the winter time.
i don't know if you have a car, but we have one so i'm not too familiar with public transport for getting there. sorry about that. i also know busan has lots to offer as well. i just haven't been down there yet. hoping to do some bouldering around there this spring. that's where the developing is, or so i've heard. as far as trad goes, i don't know of anything too close, unless you're willing to travel up to donghae, where there's some amazing one and two pitch routes at mureung valley. and there's a bus route that runs directly from the train station. if that seems like a feasible option for you, i may be heading up there in a few weeks.
otherwise, i hope to meet up with you at the crag sometime.