I didn't find this movie at all brilliant. While it had an unexpected ending and an interesting idea, I felt that as a movie it failed to deliver.
First of all it is a slow paced movie. I am an avid movie seer so I may be expecting too much of movies that I have to watch as quickly as possible so I can watch the next one. But really, the moment when you begin to doubt your initial perception of the film comes only after 50 minutes. So why did you watch the movie for so long? Only to be misled and understand what the main character really goes through? I feel this is way too much.
There there are the ghost things. I don't know what kind of ghost stories Asians have. All I am able to see is their movies. I even tried learning Japanese once so I can read the literature, but I obviously couldn't. Must all the ghosts be slimy, wet, at the corner of the eye of people that are always too scared to move so they can see the ghost and when they finally do the ghost is gone? I mean, OK, it feels scary to hear the screeched violins on the background, but that works only a couple of times. Then it is not scary anymore!
Finally , this is a confusing movie. After you think you know what the movie is about, there comes something to prove you wrong. This is usually the hallmark of brilliant movies. However, the brilliance comes at the end, with a moment of great understanding. Janghwa, Hongryeon does not provide this moment. At the end you know you got it all wrong, but however you turn the movie inside your head it doesn't really make sense.
It is not really scary and it is confusing. So, I will rate it low.