Not only the theme is dark at times, but the actual cinematography is often done with the lighting behind, so you can't see much definition in the characters' faces. Especially night scenes and indoor scenes were very poorly lit.

I did feel like there wasn't enough interaction, after the two main characters' first meeting, to justify the rich guy's level of obsession, and also that the poor guy's reaction to being sought after was inexplicably aggressive, and rude - for no reason I could fathom. That's down to the script, though.

Otherwise the film was very good. The acting excellent as expected; Kim Nam Gil never fails to deliver. Generally, the plot was interesting, and held my attention.
Overall, I enjoyed the film and, literally, wish I could have seen more of it.