Rudolf was faking his injury, he could walk perfectly fine. He just liked the attention he was getting from Kyrie, which he misunderstood as love through her faked emotions. He was paranoid about someone dying at the conference and when he heard Kanon’s scream, he rushed out of his room, not even thinking about the wheelchair. However, as he was near the end of the hall, he heard Kanon and the cousins approach. Being too far from his room to run back, he hid in either the storage room or the servants’ room (I would’ve accepted either - in both cases the gunshot got covered up by thunder).
The canon for me is the servants’ room. As Kanon, Nanjo and Kumasawa were there, and Rudolf was hidden (recall, the red denies anyone entering without anyone noticing. Obviously, if you’re hiding, it’s a different story. This isn’t really wordplay given the context of that red and the current discussion at the time - in which it was at no point discussed that someone had been hiding in the room prior – which would’ve been impossible for all except Rudolf, who wasn’t even brought up).
Meanwhile, Kinzo, upstairs, during his tantrum, as he threw things onto the wall (which was, as you’ll notice, right next to the gun room), knocked a gun off. The gun hit the ground, causing an accidetal discharge as it fired into and through the ground, and hit Rudolf straight in the head. This is not a trap by any means - it was not a contraption of any kind. It was not planned by Kinzo. There was no contraption being activated aside from the gun (which, you’ll notice, I even comment on in the thread, pretty much saying it shouldn’t be treated as such). And in the given context of the red, again, this is clearly not the scenario being discussed. Therefore, it is not a trap. In the end, it was an accident.
You’ll notice the storage room isn’t above the gun room, but I’m willing to forgive that the gun could’ve just fired off at an odd angle.
Later that night, Kinzo woke up and went to talk to Genji in the servants’ room about hospitalization. Genji and Kumasawa were asleep at the time, and as Kinzo walked in - the first thing he noticed was the smell of blood. He found the body, and upon seeing the hole in the wall, figured out what happened.
The explanation for the storage room… I don’t know. He could’ve just wandered in there by mistake? Whatever suits your fancy.
He took the key off of Genji’s belongings (or just his sleeping person, either is fine; I think a red I gave forbade me from Genji putting the key away somewhere in the room before he went to sleep oops). He then went to the gun room and put the gun back. He put the key back on the sleeping Genji and went to get Rudolf’s body.
The locked room trick is at it was described. His original idea was him framing it on a witch in hopes that his dementia would make him blur reality with his own fiction, and coupled with deteriorating memory, ultimately wipe away his sin of murdering his son. He hid in the room, hoping Kyrie would just leave and alert the others, allowing him to escape. He didn’t anticipate her being cold as fucking fuck, so he had to improvise. While she was in the bathroom, he moved from the closet and hid under the bed. After she left, so did he.
Of course, you may say - this was clearly an accident! How is Kinzo a culprit?! But I disagree - Kinzo is definitely a culprit. If you run over someone with a car, even if an accident, you’ve still killed them, have you not? If in the heat of the moment you move with a knife in your hand, accidentally stabbing and killing someone, are you not a murderer? If this plan had been done entirely intentionally, if Kinzo had managed to get Rudolf into the room and was calculated to knock the gun over, would it have not been murder then? Finally, given Kinzo’s actions after the crime, covering for it and manipulating the facts, his conscience is far from clear.
The solution could’ve been reached through the simple question of - assuming all the alibis are legit, WHEN could’ve the culprit acted? You would soon realize the culprit could’ve never entered the gun room. Once that happens, you realize the gun somehow had to go off in the gun room. That leaves with two problems - one with how Rudolf got there (he didn’t, he was in the room below, and he got there by himself) and how it could’ve been done without it being a trap (it was an accident, and the only one that could’ve caused it was Kinzo). The rest unravels from there.
Meta-reasoning would’ve helped too, I suppose, once you realize that Kanon’s entire narrative has a single significant event told in it, besides his hand injury - Kinzo’s episode of dementia.
Aaand that’s it.
If you find this solution unfair in any way, I sincerely apologize.
Congrats to solving the game!