This is an impressive South Korean movie about a serial killer. One of the first good films on this subject they made.
It has a gripping (I found easy to follow) story with good characters and acting.
The writer doesn't follow the traditional serial killer profile. Which is good because it makes guessing the killer harder.
The ending is satisfying. Not just the revealing of the killer/s, but what in their past had made them into what they had become now.
If you like Korean movies, especially thrillers then I recommend this.