Ending....*SPOILERS*

Ok so I apologize since I know there are a lot of discussions about the ending, but I want to add something that I haven't seen addressed yet.

There are several ways to interpret him looking into the camera at the end. I think two are correct. One is that he's looking at the camera as if to say "it could be any of you", meaning the killer is still at large and among them. This adds one last chilling thought to the end, since the audience is then reminded that he could be sitting beside them for all they know.

The second is that it's a sort of sad look. And I think this too is correct. In a lot of Korean and Japanese films the directors like to have the film come full circle. The film starts in the field and ends in the same spot, and while the detective's life has changed, the end scene and his sad look (as well as him returning to the scene) shows that he will be haunted for the rest of his life for not having caught the killer. So the ending, in my eyes, is a reminder to the audience that the killer was never caught (Asian films like the visual rather than inter-text like North American films saying "the killer was never caught blah blah") and to show how much it affected the detective's life that he never caught the man responsible. The penultimate scene with the family at the breakfast table is also telling, because he probes his son about video games, as if he is still a detective. This combined with the final scene are meant to demonstrate that he will never be able to totally leave that life behind him, largely because of the serial killer and how it affected him.

It is an absolutely fabulous movie, and the ending is tragic but also extremely effective. Feel free to give me your thoughts on whether you agree or disagree. Sorry if I repeated anything people have already said, I'm sure I'm not the only one to come up with these interpretations.