First, two things: Spoilers to come, so if you haven't seen this movie you might want to stop reading now.
Second, if you've seen the movie only once and are scratching your head, you're not alone.
Here's what happens: Han-ki (Jae-hyeon Jo), a street tough pimp walking along in a South Korean city spies this very pretty and privileged college girl, Sun-hwa (Won Seo), sitting on a bench waiting for her boyfriend. The girl is everything Han-ki desires. He sits down next to her. She pretends not to notice him while she talks on her cell phone to her boyfriend. When she does deign to notice him (and his desire for her) she shirks back in horror at his dirty, lower-class presumption and gets up. Her boyfriend arrives while she throws ugly glances at Han-ki. Han-ki can't take it anymore and grabs her and forcefully kisses her as the boyfriend beats him about the head. Some soldiers arrive on the scene and beat the tar out of Han-ki. As a parting gesture, pretty girl spits on Han-ki as he is held by the soldiers.
That's "the setup." It's the kind of setup that cries out for revenge or at least a comeuppance, which is what I expected. Or perhaps pretty college girl and the bad guy will find true love and overcome their social differences. What actually happens is beyond expectation in a way that is likely to stun and totally engage the viewer.
Pretty girl is at a book store. She compromises herself (in the viewer's eyes) by tearing a page out of an art book and putting it in her purse. This can be seen as the fatal moral flaw that leads to her degeneration. Han-ki sees this. (He has been following her.) Near her on the book display is a fat wallet. Pretty college girl grabs it, looks both ways, and puts it in her purse. This is the fatal moral flaw leading to entrapment and a descent into hell. She hurries to the bathroom and in the stall opens the wallet and takes out the money. Meanwhile the guy who lost the wallet is told (presumably by the bad guy) that she has the wallet and is in the bathroom. By the time he gets there she is gone. He chases after her and finally catches her. He roughs her up, calls her a pickpocket, and then forces her to go to a loan shark and sign an agreement (with her body as collateral) for money that he says was in the wallet.
This might be called "the turn" as the setup takes on a startling twist.
Next Sun-hwa is forced into prostitution by Han-ki. She makes some feeble attempts to get away, but mysteriously has nowhere to go it seems, and anyway is too afraid to run. She realizes that she is going to lose her 21-year-old virginity so she begs her captors to let her lose it to her boyfriend. Han-ki and his fellow thugs mysteriously oblige. However, the boyfriend is confused and doesn't get the job done. They pull him out of the car, slap him around, dump him, and Sun-hwa is back at the showcase on the street. Through a two-way mirror Han-ki watches her lose her virginity to a forceful client.
Question number one: why doesn't Han-ki ever speak? Question number two: why does he watch her behind the two-way mirror instead of taking her himself? The answer comes later in the film when we do hear him speak for the first time. His voice is a high shriek. Guess what his unique problem is.
And then comes the resolution. Yes, this is a love story of sorts and yes they do fall in love in a way that is debased and seemingly fated. He's a pimp and she's now a prostitute. This works out since he is able to vicariously experience her sexually and she is able to thereby serve the man she loves. And together they can make a living.
There is also a supernatural element in the film that suggests that the story is part wish-fulfillment fantasy by Han-ki. His ability to beat up the other guys and survive knife wounds fairly begs credulity. During the course of the film he loses enough blood to supply a small hospital. And the scene where both he and Sun-hwa appear together on the beach as if by magic is more mystical than realistic.
Director Ki-duk Kim's message seems to be that animal passion will win out in the end, and that humans are, despite the facades they put on, just animals doing animal-like things in the human jungle, and deliverance comes only when one realizes his or her nature and gives into it. Ki-duk Kim makes us identify with the bad guy and feel that he and pretty girl are no worse or no better than anyone else.
In short I found this movie disturbing like something from, say, novelist Cormac McCarthy. I am thinking especially of his novel, "Child of God." That title is ironic in the sense that his anti-heroic protagonist really is, whatever we may say or think, or however bestial his behavior, a child of God, while Ki-duk Kim's title "Bad Guy" ("Nabbeun namja") is also ironic in the sense that Han-ki is by societal standards certainly a bad guy, but by naturalistic (or cosmic) standards no better or worse than the pretty college girl.
(Note: Over 500 of my movie reviews are now available in my book "Cut to the Chaise Lounge or I Can't Believe I Swallowed the Remote!" Get it at Amazon!)