I will not give anyway anything about the story, because it's such a great experience, watching this and getting more and more details about the background of. I'm not saying there are really exciting and surprising twists and turns, it's not that kind of movie, but you certainly are stunned when another part of the story is revealed. There may be "too many endings" as another user pointed out in a comment, but it still worked for me. None of the final scenes is unsatisfying, even if you maybe get the feeling that it's just "too much".
What makes this movie so special is the topic it is dealing with. It is not just a police-murderer-story, it reveals a shocking look at the Asian education system with all the pressure students have to deal with - teachers, parents and fellow students - and the brutal consequences. It works as a political/social movie, it works as a police thriller and it even works as a comedy, because the two cops that are supposed to solve the case are just funny as hell. It is sometimes strange to experience the fast change between really funny scenes and sad, dramatic moments, but then you realize that this is not that different from the real life.
I was really impressed by this movie, by its humor, its deeply touching scenes, the brilliant actors and the beautiful cinematography. It deserves a larger audience than minor festivals.