Let me give this 10 because they're brave enough to offer this kind of movie. For me, this is a new kind of Korean movie I've seen so far. They give a special touch of sci fi movie which not as Hollywood presents.
Not just about a sci fi action to run your adrenaline or entertain to watch, they try to touch the heart of the audiences.

They start the movie with an intense plot, get into the middle with swing the audiences' emotions then end the movie with a twist yet reasonable decision.

The acting of two main characters are truly the power of this "heavy" movie into the enjoyable one. They got you hooked and emphatized with their stories. I expect more for some roles development and action scenes. But it could take more than 2 hours, so this should be enough.

A movie with good details, philosophical dialogues, nice CGI, proper action scenes, good timing of humor and superb acting wrap this movie into a unique one.

After watched the movie, I could't stop to think of the scenes and dialogues which somehow gave ache in my heart.
Human, life, and death. Thankful for this meaningful movie.