f this is true, I have a theory filling the gaps:
The game said nothing about an individual traitor, we only thought so because the rules were short and the action started immediately. They say that one person (an attacker) wakes up, and that "so basically, there's a traitor". If this is the case, it doesn't imply that just one person is a pure traitor. However the game still says that "the attacker will be given a time limit within which to kill exactly one person."
Since you have to kill one person, 3 people have done so in the 5 episodes. I assume that they are given some crucial threat when they wake up, so that they are convinced to do it. They might also be told they could kill themselves to end the game right there.
Tengan becomes the first attacker, he decides that the only way to truly motivate people is by killing Yukizome
This is why he brings it up specifically while fighting Munukata
After the second killer is waken up, he is still out cold. He figures out that this means the killer changes each time.
Aoi is the second killer, she kills Gozu
She is the one who does the fake knife trick to make people think she is innocent
In a nervous panic, the other two don't think anything of it
I'm not entirely convinced that Aoi did it, and people bring up a good point of Gozu trying to game the system in order to not have to be killed. I feel it'd be too obvious if Monaca did it though. She might just be more a person to make sure rules stay in check.
Tengan tells Munukata about the game's secret, he's stunned because he realizes that Tengan killed Yukizome then.
He decides that he needs to live longer, not letting the secret die.
He kills Seiko for the drug that saves him, tense why he uses it post credits
Mainly reposting to trigger discussion about it.
