What's Inside Kim Moo Young's Head?

Is it the age old Sociopath vs Psychopath debate, is he extremely eccentric, or just misunderstood? Anyone who's up for debate regarding the psychology of the show and our Protagonist's (or is he?) mind is welcome! Comparisons with Kimura Takuya's character from the Japanese original can also be made (Please remember to mark your responses with the spoiler tag though.)
Ciao. :)