In desperate need of an ASIAN film title! Serial Killer Hitchhiker ?

OK, I'm really struggling to remember a film I started watching about a year ago, so if anyone can help out, I would be most impressed!

alrighty... I'll be honest, I can remember f*ckall about this film, but here goes....

This is all i've got to go on, unfortunately

It's about a hitchhiker who is a serial killer, and murders those who give him a ride.

And the driver who picks him up is ALSO a serial killer. (at least i think it went like that, anyway...)

So of course,each man is secretly planning on murdering the other. (again, I think...)

It's definitely an Asian film (Sth. Korean perhaps?)

I'm positive it was in the last ten years

i know it aint much to go on, but any help would be greatly appreciated, as I really enjoyed the small part that I saw, and need to see it again :)

and please, have a wonderful day