Right from the start Joon-ho sets up the movie to be more of a character study and exploration of the three detectives, especially detective Park Doo-man who is the main character in a somewhat big cast. While exploration these character, Joon-ho also explores the murders, their aftermath and how lives and towns are affected with just heinous crime. How a group of lives (the people investigating the murders) can be so drastically altered when dealing with such a crime. Joon-ho does a beautiful job exploring these themes through a complex nuanced filter that never puts judgement on the murders, characters and the situation they're all in. Joon-ho puts the situation in our face and it's up to us to, not the director, to judge.
Just as Joon-ho explores some hefty themes, his characters are just as interesting as the themes. The two local detectives, while have good intentions, do some shady shit and are completely under-prepared and overwhelming. The first "person of interest" they get in for interrogations, they get him undress to his underwear and detective Yong-koo starts to kick the living shit out of him with his steel-toed boots. Both local detectives verbally and physically abuse the suspect and try to put words in his mouth to make him the killer. But then we got to one of my favorite scenes in the movie where we see both the detectives and the suspect eating cup noodles together watching an old cop drama tv show. They both talk about how great it is and the detectives are treating the suspect with a love and care that you see small town people tend to do with each other. A few minutes pass and then the detectives go back to verbally and physically abusing the suspect again. Thinking more of this scene, it really encapsulates the two local detectives: who they are and how they try to solve the crime. Now these local detectives aren't simple folk or stupid, but just two somewhat regular people caught up in something that's so far over their heads they don't know what to do or where to start. And Joon-ho never puts judgement on them or any of his characters, he just shows them as they are and here's what they do.
Joon-hodoes a bang-up job with this movie especially with his eye for composition. Jesus Christ, this is one beautifully shot film. Not only is it beautifully shot but it has some of the best long takes I've seen since Children of Men and some of Malick's & all of Tarkovsky's films. Just the way he positions certain characters in a scene or how he uses the landscape to add a layer to the film; it's beautiful to see.
This is a masterpiece movie that is an emotional roller-coaster and will get burnt into your memory.
Luckily for you and thank god for internets and youtubes, you can watch the entire film on youtube! And in high quality. But if you like, remember to buy it.