This keeper thing is starting to become a problem to me. I don’t know, some points in the story sound like he is in fact the key keeper and some points don’t (to me).
If one thing is certain is that Kanon was the key keeper from begin to end, he couldn’t have become the key keeper at some point in the middle, due to the narration rules. I think we all have to agree on this.
Kinzo was the key keeper:
[Color=blue] Kinzo left the study after seeing the telephone lines were cut, so he could find the killer and take him out. The killer found him first and killed him, taking the key afterwards. The shot wasn’t heard because the weapon was silenced. The culprit didn’t take the key from one of Kinzo’s pockets, so he didn’t ‘pickpocket’ him, the key was in another part of the body when Kinzo died. He entered the room, took the vial and left the study. The voice everyone heard was a recording, even if it was indeed Kinzo’s.[/color]
The weapon was silenced this time, but not when Kanon was shot. There is a reason for this. The culprit didn’t want people to discover of this Kinzo’s voice trick, while he wanted everyone left to hear Kanon being shot. Or maybe he thought everyone in the house was already dead, thinking Kanon didn’t make it in time to save Battler, so he didn’t care about it anymore.
The key could’ve ended up in another part of the body due to the impact, or could’ve fallen to the ground, there are some variations of this (when talking about the pickpocket part).