Furthermore, although a red truth forbids poison gases (“There was no poison gas, there was no drowning, there was no death by suffocation!!”), I still presume most of the victims’ food or drinks were drugged to make Yasu able to overpower them. Also, the Red Truth says nothing about gases that do not cause death, or substances such as formalin and chloroform that could possibly knock out the person, or at least disorient them to make them easier to deal with.
Six bodies were found in the tool-shed, their faces smashed apart, with a magic circle on the shutter. The six were Krauss, Kyrie, Rudolf, Godha, Rosa and Shannon. Out of the six, only Shannon was surely identified thanks to her ring. The shed was locked by a key that was in the servants’ quarters.
The method of the murder is irrelevant. Based on the blood-stains in the dining hall, the actual killing caused only minor bleeding, so it was either a relatively small stab wound, or, more likely, blunt force trauma directly to the head. Either way, the end result is the same.
The faces were destroyed to protect Yasu’s identity as Shannon/Kanon and to keep the modus operandi consistent. It is also notable that neither George (the person closest to her who was not in on the murders) nor Battler (our only reliable narrator) have seen her face, only Hideyoshi.
However, it is quite possible that Eva and Hideyoshi are forced or bribed into becoming Yasu’s accomplices at this point, thus it is not only possible that Hideyoshi lied and Shannon’s corpse weren’t even there, but highly probable.
The funniest thing though is that the Red Truth regarding unidentified corpses specifically allows Shannon’s corpse to be non-guaranteed. One one hand, it is described as being only half-smashed and thus she was not “unidentified”. On the other hand, there was no “corpse” to begin with (as in, Yasu was either still alive or there was no body at all to begin with). In short, Yasu dodges the Red not once but twice!
Maria’s involvement was made especially obvious by the magic circle, which was more than likely drawn by her on the first place, thus explaining why she knew so much about it. The same goes for all the other magic symbols throughout the episode. The circumstances relating to the shed’s key and the locked mansion doors are irrelevant, as the servants have the keys for both.
In the morning, Eva “sealed” the door to Kinzo’s study with a receipt so that she would know if the door was opened afterwards. When they later enter the room again and Kinzo was missing, she questions Natsuhi about how Kinzo could have disappeared without opening the door.
Kinzo was never in his room to begin with, so there was no-one to leave on the first place. I think it is pretty self-explanatory.
Eva and Hideyoshi were killed in their own room. They had to cut the door-chain to get inside, and in there they were found with stakes in their foreheads. Eva was on the bed, out of view from the door, while Hideyoshi was in the shower.
The method of the murder is, once again, irrelevant. It was shown that, through the unreliable narration, the servants could have murdered the two any way they wanted to (though Yasu probably just shot them) and then stake them and position their bodies however they wanted.
The stakes were drilled into their bodies postmortem, or rather they were played in the gun-wounds, the effect is the same.
The closed room is solved by the unreliable narration. Contrary to what is “shown”, the following is what really happened: They opened the door with the master key, Kanon cut the chain, they killed the two, and then pretended to find the corpses alongside the rest of the family and that they only just recently “had to cut the chain” to get inside.
Kinzo’s body was found in the furnace of the boiler room, with a stake in his forehead. His body was charred and could only be identified by his extra toe.
Kinzo was not murdered, he has been dead for a while thanks to natural causes. His body was hidden in the furnace and was recently doctored by adding the stake to his forehead.
Kanon was found on the floor of the boiler room, bloodied with an apparent wound on his chest, with the bloody stake next to him.
Kanon wasn’t murdered either. He faked his death with the help of Nanjo’s fake diagnosis. No one has actually seen him being stabbed, with the stake in his chest, and people only judged how serious his injury was based on the bloodstain on the stake. There is no objective observation about him being actually wounded.
Everyone is locked in Kinzo’s study, when a letter appears on the table while they weren’t looking.
Maria put the letter there. She was the one who pointed it out on the first place, and the goal of the letter was to single the accomplices out so that they could get out of the study.
Genji’s, Kumasawa’s and Nanjo’s bodies were found in the lounge, their faces smashed and the bodies mangled. Maria was found facing the wall and singing, and she says she was told to do so by the witch. The door was locked from the inside.
The three were killed by Yasu. It is entirely possible they were drugged beforehand, though not necessary. Maria was on the sidelines during all this.
The door was locked by Maria from the inside to create the illusion of a locked room.
Natsuhi appeared to have had committed suicide by shooting herself in the forehead in the hallway. It appeared there is no one left on the island who could have done it.
There was more than one gun to begin with, and so Yasu was easily able to kill Natsuhi while the cousins were locked inside the lounge. By the time they got out, Yasu was gone, replaced her gun with the killer weapon, and so it appeared that Natsuhi shot herself once the cousins found her.