"Insane" isn't a bad movie, but it isn't one of the best neither. I will start with the good parts first.

Firstly, the acting is great. I have been a longtime fan of Kang Ye Won. She is a very strange character indeed from what I've seen on variety shows. She was, without a doubt, the star of this movie. Her performance was really captivating and raw, making all the horrible things seem real. Lee Sang Yoon was great as always but this time he was overshadowed by Ye Won.

Secondly, it deserves its thriller genre, tipping its toes in the horror genre as well. It was disturbing and scary because I associated with real events that happened in this world and I knew they weren't far from what this movie shows. It doesn't shy away from relating the more gruesome scenes, even if it doesn't show you directly what it's happening - imagination can be richer.

On the other hand the plot kind of disappointed me. From the 3rd act, it seemed kind of rushed and confusing - like the writers didn't know what to do with the story. It had some plot holes and I would have loved to have more things developed with some side characters that were pretty interesting: like their motives and backstories (Mi Ro, Nurse Han, and Kang Byung Joo and The Doctor).

Lastly, Ye Won and Sang Yoon's characters were a bit too different - or more their storylines. They had their interactions but unfortunately, they left me cold...they were better alone on the screen than together, which is a pity cause they are both great. I think the writers could have used those scenes better to add more tension and mystery so maybe the ending would have made more sense that way.

All in all, I enjoyed it. Do I recommend it as a must-see? No, I don't but if you are a fan of one of the actors or of thrillers in general give it a try because probably you would enjoy it!