There will be a 5.10 climbing festival at the Songam Spots Town in Chuncheon to celebrate Buddha's birthday (10th May). Apparently, despite his bulky frame, he was really into climbing.
All the details I have are on the link above, but it's all in Korean. From a quick scan, it looks like there are lead, speed, bouldering and dyno competitions and you have to apply before the end of April.
The local sports crag (Eui Am Am Jang) and ridge (Chuncle Ridge) are about 2km up the road and have ample space for camping.
I think there's also other X style competitions happening on the same day. BMX, Skate boarding, disco dancing, rollerskating, dominoes... you know, that sort of thing.
If I get any more details, I'll post them.