The real killer SPOILER
Well, i read a lot of thesis about the real murder. I read, also, that the real importance of the story is the story in self, no find the killer. but we can try to find him anyway. Ok.
The killer is the detective Cho Yong-koo(actor: Roe-ha Kim)
The killer is all shaved.
Has fine hands.
Goes crazy when the song starts.
Burned the face of the retarded boy.
--->Now find this things on Cho Yong-koo.
When the song starts in the police station he is not there.
When the song starts in the interrogation room, while everyone waits the reaction of the accused, he, Cho Yong-koo, looses control and jumps over the accused.
He has fine hands, obviously, because he has a office work, just like the last accused.
He knows every girl on the town because he grown up there.
THe retarded guy is afraid to him because: 1, he burned his face and 2, he murdered the girls.