A very cool story-driven game. I absolutely love the music, it really fits into the narrative.
There are a few things I want to point out however:
1/ There is a lack of visual cue and clarity on where the player should go.
2/ Regarding the story, there are too little build up to this point in the story. Consider adding previous chapter than explain the characters a bit (with the same mechanic)
3/ The mechanic has no thematic ties to the narrative.
One strong point of story-driven games are the intersect of narrative and gameplay. Rather than finding keys, why not make the man stab the someone and steal their life force for example. That will put more emotional and decisional weight to the player's action
Sorry if this feels too overwhelming, I don't usually write this much but I really love story-driven games.
Overall, a very cool concept and story. 3.5/10.
P/S: Don't be discoutage by the score, it is reflected the game quality, not potential.
You can send me your future update and see the scores go up!