I'm glad this show gets here recognition and so much love because it really deserves it! Everything was amazing, especially the characters' friendship in the past and in the present as well. Thank you show for giving me so much emotions (and Seo Hwi Young <3)
Unless I watched it wrong, this movie leaves room for viewer interpretation of the ending. This is what I got…
That's also what I think, I had noticed the same clues as you. The way the shaman acted at the end of the movie makes me think they were actually working together, or even possessed by the same evil spirit. I've read somewhere that the girl in white may be actually a shaman possessed by a good spirit who wanted to protect the family but couldn't because the policeman tried to kill the Japanese man. However, there is one thing I'm not sure about... what happened to the policeman at the end? Was he hurt? Is he still alive?
Enjoy~~ <3