Responses
So far with the title and all the killings, the hand needs the mirrors to travel. I use to think the mirrors in the house were special but i think the hand just needs mirrors. Even in the movies, the other side of the window was a mirror. Maybe I'm dumb and didn't realize this sooner. But wanted to put that out. Mirrors trap souls or they reflect the dark side. So I think this is what is happening here

Was Joon's reflection smiling what does that mean.......