Oh, if only I wasn’t preoccupied for pretty much all of today. I’d love to delve deep into this gameboard, but alas, I must restrain myself.
Still, I might as well throw something quick at you to get things started. Since Kyrie did not see a pistol in the crime scene, suicide can be ruled out for now. Naturally, a person who shot themselves in the head would have no opportunity to conceal the gun. Using some kind of remote mechanism might be possible, but since Kyrie saw no traces of any such mechanism, it seems highly unlikely.
What could still be in the realm of possibility, however, is that Rudolf was not actually dead when Kyrie woke up. A convincing makeup might have fooled Kyrie. So, let’s try out the following.
The closed room was created from the inside by Rudolf, who was not actually paralyzed. The car accident may have been real, but Rudolf’s injury could’ve already healed, but he decided to remain in the wheelchair and feign being paralyzed for some purpose. He then pretended to be dead until Kyrie woke up, investigated the room, and left. After Kyrie left, Nanjo entered the room and killed Rudolf. As Nanjo must’ve faked the autopsy in this scenario, this would mean Nanjo is the culprit, as there can be no accomplices. Rudolf does not count as Nanjo’s accomplice in his own murder, since even if he acted on Nanjo’s instruction, he did not know Nanjo was planning on killing him, and thus did not ‘knowingly help with the culprit’s plan’. Rudolf was under the impression that the whole fake murder was for a different purpose.
Alternatively, to borrow from my own book… Rudolf created the closed room as described above, put on the makeup and everything, and then died from poison. As Nanjo examined the body and he would’ve noticed the bullet wound is fake, this means he, once again, is the culprit, but he didn’t come kill Rudolf personally after Kyrie had woken up. Perhaps he offered Rudolf what was supposedly a drug that makes him convincingly appear dead, but was actually poison that killed Rudolf when he took it after finishing his preparations after Kyrie had fallen asleep.