Part 224: (Hint 16)

"It was impossible for Maria to commit any of the murders in the guesthouse. So, the most Maria could do was kill Shannon."
"Which means a third culprit would be needed for the guesthouse murders."
"The third one would have to be Eva, Hideyoshi, Rudolf, or Kyrie. And that would mean we'd need a fourth culprit too, right?"
"...You're right. In order for one of those four adults to play dead, the child who checked them would have to be a culprit too. In other words, if Maria is a culprit, we'll need to have at least four culprits total."
"If there are four culprits, then each one of them must kill at least one person."

The definition of 'culprit' is a murderer.

"...In which case, things don't quite seem to add up."
"The four culprits would then be two adults and two children. One adult is in charge of the murders on the first and second twilights. The other adult handles the murders from the guesthouse onwards. Yes, that creates a contradiction."
"A culprit is defined as 'one who murders'. That means anyone who's a culprit must commit murder at least once."
"Simply put, there are very few people that a child culprit could murder. The children could not have killed in the first and second twilights. They also can't commit murder after the first deaths in the guesthouse take place. The only one they can possibly commit is Shannon's murder on the fourth twilight."
"...A child culprit can only kill Shannon. A second child culprit couldn't kill anyone, so they couldn't be a culprit at all. It means there can be only one child culprit."
"As soon as we pick Maria as a culprit, we need another adult culprit besides Rosa. However, it's impossible for there to be a second child culprit to lie about their parent's death. In other words, it's impossible for Maria to be a culprit...!"