Hey I live in Seoul too and am always checking out CL even though I bought a new bike already lol.

I think you can do well to get a new bike here, have it fitted along with the free service and other goodies thrown in. I see people selling used bikes on CL for almost the same as the going rate new. There's also a guy selling multiple bikes from different locations who never gives his phone #, I suspect those are stolen. I know of at least 2 different bikes he was selling listing different locations as he called my friend back on both. Be careful and see u at the Han

*edit - this seller seems legit, I wonder what size the bike is. He seems to be on the short side based on the saddle height.