This is an extremely good film - highly recommended. It will not be to everyone's taste, but if you are not afraid of thinking during a film then you should find plenty to take away from this one.
Bad Guy is a film based on the central premise of a relationship built between what is effectively a hostage-taker and his hostage. What transpires is a stream of abuses, power-shifts, emotional turmoil, love, hate, violence, sex, and almost every other aspect of life. This is an extremely original story, well told, with fascinating characters that are extremely human... both the good and bad sides of humanity.
The production values are very high, great acting, direction, cinematography, script, music, everything is top notch.
Typically, Korean films are very much based in real characters, social issues, and have an earthy approach that humanises their films beyond those of most countries. Bad Guy is no exception... while it is violent, confrontational, and decidedly dark, it bristles with underlying emotion and shows life without the rose coloured glasses.
The characters are at times extremely emotional, and at others almost entirely emotionally void as they struggle constantly to keep their balance in circumstances that are spiraling around them.
This is not an 'easy' film, in that it does not hand feed the viewer, there are no 'Jaws' style music queues to let you know when to be scared. You will need to work out how to feel for yourself with this one, which is fairly rare in this day and age.
As said earlier, this movie is not for everyone, however if the concept sounds like something that interests you, then you should enjoy this film. If on the other hand you don't like the idea of watching a film based on the idea of a man forcing a woman into a life of sexual servitude, then stay well away from this film.