when we went to Hongdae for the gig we had some time to kill, so we visted this op shop / second hand shop we found online.
there are lots of flee markets in Seoul but not many op shops, so we were really excited!
it's called Object Recycle. (there's a map under the tab MARKET, click object store)
they not only sell second hand stuff, but also some original products of their own. some artists also sell postcards, bags and etc.
i didn't purchase anything but there were certainly some very interesting things to see, like the Bratz dolls with very seductive looks: