Created an account just to give this masterpiece 10 stars.

Rating: 10/10 (5 May 2020)

Obviously a poorly written critic from me is unnecessary. I just signed in to give it a 10 (originally gonna give it 9, but) to justify the poor 1 star rating who obviously given by someone who doesn't even enjoy a thriller/action Korean movies or even movies from this kind of genre.
If you enjoy a crime/action/thriller movies you should definitely watch it.
If you like Korean movies, give it a try and you'll probably find a love for a thriller genre...
And IF, you love Korean thriller movies, then this is a MUST WATCH. period.

(side note, call me crazy but i will mark reviews below 6 with "unhelpful review". it is very unjustified for reviewers who are not in the same page with this genre mindlessly make baseless review and to even call it a "taboo". no one forces anyone to watch a movie with genres they don't like)