Like the concept, but I feel the execution could've been better.
Found a way to cheat the system: just stand in front of the main door and wait for the red bar to move. Since only one NPC enters at a time, it's easy to spot the real ghosts that way, which kind of ruined the gameplay.
That said, I also played it as intended, and it was fun! Really like the art style, and the music fit well. the ghosts turning slightly transparent was a nice touch.
Adding an outline around the NPC you want to kill would be a great addition.
Great job either way!