I accept your challenge, @Aspirety!
I have several different theories that I think could work, so I guess I’ll go through them all?
Maria did it; Kinzo did it; Natsuhi did it; everyone did it; Beatrice did it. I could have technically been most of the first 8 who died too, since I dont trust Nanjo, and the scenes were not really inspected at all.
Since I doubt there was DNA testing at that point, we could assume that all the bodies were completely mangled by the murderer afterward, and the police could only “identify” based on the right number of bodies being there, minus the children. As was stated in-game, there is the possibility of a body double for pretty much any of the dead.
No one! In all of my theories, this is the only thing I can come up with. Obviously if Maria did it, this one wouldnt need solving (although Im not sure I like saying Maria did it, since that seems too obvious… but maybe its reverse psychology).
However, if Maria didnt do it, then here’s what I think happened: Maria never says "A person walked up to me and gave me these, and that person’s name is Beatrice, does she? IIRC, she only ever says “Beatrice gave them to me.” So I propose that Maria simply found them in her bag (as Battler originally thought had happened, heh), probably with a note saying “Open this letter after dinner -Beatrice”. Since Maria was already so convinced that Beatrice existed, and she didnt remember putting them in her bag, she would never even question the “fact” that Beatrice must have put them there. Of course this means that the real culprit snuck them in there at some point, which could have happened at almost any time.
If you’re asking “with what weapon”, I honestly dont know; it could be anything since the living didnt really investigate the bodies.
Anyway, I think anyone could have gotten into the storehouse easily enough, especially since Gouda was killed. As for how they took down six people… I bet the six people split up. Shannon was by herself, and distracted by thinking she saw butterflies. Gouda was by himself, and we saw that he wasnt being too diligent. I think its plausable to say that after Eva left, the other 4 decided to take a break/go to sleep. So they probably split up too, all distracted by the heated conversation they had just been having.
This was my favorite one to solve, although my theory is pretty close to what @Seraphitic already said, although I thought it out a bit differently. Obviously if Eva and/or Hideyoshi were the killers, this one would be solved easily: one/both of them faked their death(s) (and killed the other), make sure the door’s locked, no one inspects them very well, bingo.
Havent thought this one out for Maria, but I guess its possible that no one noticed she was missing? For just a bit… this one is honestly the most unlikely for Maria to have committed, and could be the deal breaker on that.
If it was Natsuhi, since she prepared the room, she could have conceivablly set some kind of traps.
If it were Kinzo or anyone else, it could have either been basically as Seraphitic said, or instead of being in the room before Eva/Hideyoshi, the two had only locked the handle and not used the chain. The murderer came into the room after them (obviously, as established in-game, they have some master (set of) key), kills them, then relocks the door with the chain to make it seem like a closed room, and hides. Just like with Kinzo’s closed room, no one really inspects the scene all that thoroughly.
Wooo this was the hardest one. It could be Kumasawa… but I dont like her for the Eva/Hideyoshi murders since she was in the kitchen with Genji, Kanon and Nanjo.
My theory is: he killed himself. Kanon obviously knew about the Demon’s roulette, as he was talking about it. I say that his “act of rebellion” against the witch who he believed was in front of him was to take his life into his own hands instead of letting her kill him. After all his promise he made to himself was that he’d “sacrifice this life of mine and bring this roulette of yours to ruin!” The roulette wouldnt be killing at random if he killed himself, and he would be potentially saving someone else from being killed.
I propose that what he picked up off the shelf was not the axe, but the demon spear. After all, although we read that he dropped the axe while no one else was in the room, once everyone else comes in, the axe is never mentioned, as if it wasnt actually there.
Could have easily been Maria. Also could have been Natsuhi, since no one was accusing her for obvious reasons. It could have been on the bottom of a food can and thus someone outside the room could have snuck it in, but I dont have any specifics for that.
It also could have been Kinzo. Of all the bodies, I think Kinzo’s most easily could have been the double. The only way he was identified was through his double polydactyly, which I think either could have been replicated onto the double, or it was one of the earlier bodies, who could have also had polydactyly, since it is supposedly common in the Ushiromiya family. And the key that Genji found, also could have been fake (or Kinzo had more than one) and it was put on the body to make them think they would be safe in the study.
Kinzo could have already been back in the study. When Battler started screaming about the epitaph, everyone did look up. The four who are accused are only accused by Natsuhi; it is never said whether or not they actually didnt come over to the portrait too. If Kinzo were hiding in his study, he could have slipped it there while they were distracted. Of course, this also requires him having a good enough hiding space that no one found him the whole time, even after the first four left.
Ok I change my mind, this one is the hardest. It could have easily been Maria, but as I already said, Maria just doesnt seem like the killer to me. This is the one that kills the Natsuhi suspicion for me, since she was obviously with the other kids the whole time…
Kinzo could have done it. Not sure how he would have convinced Maria to say the right thing again, but I guess it could have been another note. Especially if he included magic circle stuff, a simple not could probably be very convincing to her.
Three guesses. 1) She is the culprit, she faked her death. 2) The note said something along the lines of “kill yourself, and your daughter will be spared.” 3) The gunshot wasnt hers. @Seraphitic brought up how the cartridges of the gun seemed more important than the gun itself. No cartridges were mentioned when the kids found her, so maybe it wasnt her gun? (This doesnt necessarily mean that there for sure was no cartridge there though, since they could have just not noticed, or Battler didnt think it was an important thing to mention in his narration amongst everything else going on.)
Oh wait, I forgot about the “everyone did it”. Okay, this is definitely a stretch, but my theories about Kanon and Natsuhi killing themselves made me think of something ridiculous: what if everyone committed suicide. You know, what if they all slowly started believing in the witch, and decided, like Kinzo, that they should all try to revive her? I dont know, it is probably the most improbable theory out there, but is it really impossible? I guess it wouldnt explain the children missing at the end though, heh.
OK. DONE. That took WAAAAAY too long, haha. It was fun to think about tho. I dont think I came to any specific conclusions, but hey, its only chapter 1. Now, go ahead and confuse me by pointing out all my errors and pointing me in the wrong directions!
I’ll probably want to talk about the Tea Party and ??? later too, but that should definitely be saved for another day.