I watched this movie on local TV (meaning it was dubbed) and thought I share my (unpopular) opinion about it.
While I agree with the majority saying it's a good movie I can't say I enjoyed it much.
Maybe because the style of the director is not my cup of tea. Maybe because I find the things that happened throughout the movie a little bit too much on the disturbing side. I know what I signed up for but the overall feeling of the movie is tense and there is no happiness at all. It does contain a deeper meaning though so the violence comes with a plot. Otherwise I would not have watched it.

The story is focused on the main protagonist Gang Do who visits debtors to collect the money and if they don't pay, beats them up, threatens them or even goes beyond that. Mi Sun, the mysterious woman who claims to be his mother seems to be calm and gentle and despite his aggression and violent behavior stays by his side. The whole story has a plot twist though because Mi Sun carries a dark secret.
The cast does a good job. For me Jo Min Soo stood out the most as Mi Sun but Lee Jung Jin could also portray Gang Do believable.

I didn't pay attention to the music so I can't say anything about it.

Rewatch value is low. I do recommend watching the movie once, for the messages it contains and because it makes you think but one watch is enough for me.