Surprised at the amount of confusion

Well she was dressed in white for a start - always a good colour for those pure of heart!

And she was throwing the stones - "He who is without sin cast the first stone".
That was when it clicked for me!

Its uncle Frank Kirsty!
Its time to play!

Soon, we will all have special names!

Well she was dressed in white for a start - always a good colour for those pure of heart!

And she was throwing the stones - "He who is without sin cast the first stone".
That was when it clicked for me!

Who knows maybe the director had totally different ideas - you never know with different cultures!

Its uncle Frank Kirsty!
Its time to play!

Soon, we will all have special names!

I totally agree with blueyoke, to me the white chick was the mastermind and the japanese, another shaman who was being possessed. he clearly had struggles with the evil force growing inside him.( waterfall meditation scene, crying scene when he was being followed,etc). the girl in white later got him killed so that the daemon finally gets a true physical form. keep in mind that the white chick also lied to the policeman about seeing ppl getting killed by the japanese.

the young shaman despite how the movie tries to portray him as a fraud was the good guy all along(remember this is a movie where everything is different than it meets the eye), he was clearly hurting the possessed shaman during his ritual,(if it was the white girl, why did the hurting stopped when the ritual was interrupted?) he warned the policeman about going back to her daughter as soon as possible when her girl was getting ready to go on a killing spree, he warned the policeman about interrupting the ritual and the possible backfire which is what happens later in the film,etc.
do you guys seriously think that a good force would cause the evil throw up blood?

*Spoiler*

I agree with blueyoke. There isn't enough information to conclude that the woman in white is good.

I also agree with what other posters say here that the Taoist shaman was also as ambiguous. In fact, the photographs thing seems to be a moment of opportunity for him as a shaman, paralleled with the Japanese Man taking a photograph of the priest.

The only certain thing in the relationship between the Japanese Man, the Taoist and the woman in white is that both men fear her immensely. However, she has no similar effect on other humans.

There are four things that seemed intriguing to me:

1. The woman in white is present during Hyo-jin's transformation. She also implied to Jong-goo that she was present during another killing earlier on, the one where an old lady suffered the most. (She lies to him about the Japanese Man sucking the blood of him victims, though.) This makes me lean towards the conclusion that she is related to death, which would explain her constant presence around the Japanese Man (for he is a ghost, as it is repeated many times). It might also explain the Taoist's reaction when he came close to her.

2. Jong-goo's colleague went through the transformation without us noticing him being a target for the Japanese Man. No belongings of him in the secret room.

3. Building on that, the Japanese Man was in fact so focused on Chung-bae, the man who comes back from the dead during Jong-goo's raid with his friends. He never appears to be actively targeting Hyo-jin at any point of the film's running time. Even in the cave, he wasn't doing a ritual like the one before, but rather 'recuperating' in a sense. In fact, the only things that link him and Hyo-jin are her shoe, which was taken away from him, and when she nodded to her father when he asked if she'd met him. So it is more likely that he wasn't the one going after her at the end.

4. Hyo-jin became ill when she contacted the Japanese Man off screen. She became worse when the Taoist did his rituals, even though the Japanese Man was dying. When he later died, she became better. Then she met the woman in white, became worse and went on to kill her family. She had contact with all three characters, and became worse after each time.

From these four things it is not illogical to conclude that the Japanese Man, the Taoist, and the woman in white are all competing in the village. They are all trying to outdo one another, and they use innocents to try to kill one another whenever possible. I guess that would make all three of them evil.

[Edit]

I have watched it again the other day. There are two very brief scenes that partially altered my view.

When the Japanese Man falls off the cliff and sees the woman in white nearby, he actually musters his strength and chases her (scene 1). A few minutes later, the Taoist is looking from the window and mentions how Jong-goo is an idiot who took the bait. The very next scene is of the woman in white looking over as Jong-goo is finishing off the Japanese Man, as if she is the one who'd cast the bait for him: she gave him the Japanese Man to kill, and thus commit a punishable sin.

The other thing that caught my attention is Hyo-jin's drawing of the Japanese Man's true form prior to her first symptoms.

All put together would make the sequence as follows:

1. The Japanese Man shows his true form to a person. The person develops symptoms.

2. A shaman is called upon to intervene. It back fires, though, and symptoms get worse. If a shaman is not called upon, symptoms still get worse.

3. The woman in white encounters the person for a last time, turning the person and their entire household into a trap for the Japanese Man. She is the one responsible for the massacres.

Conclusion: the Japanese Man wants a person. The woman in white uses the person and the person's family to try to get to the Japanese Man. The Taoist uses the person to try to get to the Japanese Man, and get rich in the process, since he is seemingly the only human party here. All of them are evil.

Are they in it together? Maybe. That would explain why the woman in white and the Taoist are trying to kill the Japanese Man without incriminating themselves: to set themselves free.