Why is Mayu still with the staff? She played the game and sacrificed herself, so shouldn't her arc be completed? Why hasn't she been either cast into the void for losing? Also it's apparent that Ginti isn't that fond of her, so why even keep her around?
Losing doesn't mean being sent to the void. It's determined by a test of character, not if you win or lose the game. If anything, sacrificing herself would mean that she'd get reincarnated. She probably just refuses to leave and Ginti is too much of a pushover to do anything about it except yell a lot. Or he could have had her judgment period extended since he finds her to be odd for a human.
Because he has no idea how to judge her. He admits as much in episode seven; he tells her something like "everything's gotten messed up since you came along." Then when she says that games in which you pit two people against one another are stupid anyway because people will always "look out for number one," he remembers her Heroic Sacrifice and asks "what about you?". During the Twister game, he gave a Slasher Smile when Harada was about to push Mayu, fully expecting him to do it. Then, she took the fall for him instead. He probably never saw anyone sacrifice themselves for the other player even before realizing they're dead before, and even her reaction after realizing her death probably came from left field as well. He's never met a human like her, so he has no idea how to judge her. The summary for episode 11 seems to be implying he's going to do something about it.
What exactly was the outcome of Nona's experiment with Decim, and what did Oculus end up doing about it? We see in episode 12 that Oculus finally confronts her about this, casting the whole experiment off as ridiculous since "Arbiters are dummies and can't have emotions", but he doesn't actually do anything about it. Nona just simply explains her experiment and walks away, leaving Oculus with a seemingly confused look on his face. What exactly happens afterwards?
That confused me too. My best guess is that it sounds a lot like a Sequel Hook that will be explained later (maybe). There were actually a lot of holes and it feels like there might be more to come because weren't they in the middle of a death crisis? We never hear anything about it whether if it got better or worse.
Oculus, at the end of Episode 12 basically made a new rule, which was essentially "Arbiters can not associate with humans", or something similar.
I had assumed that was just one of the rules from the beginning, which hadn't been outright stated until episode 12. They made it seem like they were hiding the fact that Onna was even there the whole time (nobody knew about her except Nona, Clavis, and Ginti). What I took from the ending was that it didn't really matter anyway, because Nona's plan wouldn't do anything to change things from "business as usual". It didn't change anything, so no need to "correct" it.
So.. any reason why Chiyuki knew that she was dead upon coming to Quindecim, or was she just special for some reason?
Based on Nona's dialogue when she comes down, it's the person who compiled and wiped her memories just made a mistake, so that she still knew she was dead and had the mindset she had when she died, but not any memory of the actual events.
It wasn't a mistake, and Chiyuki wasn't necessarily special or anything. In the last episode, Castra asks if they should keep forwarding the memories of their death to their guests. Chiyuki having kept her memories was simply Nona's doing, but she's an expert at keeping secrets, so she probably just told Decim it was most likely a mistake to dissuade further questioning.
Why do they keep on saying that Arbiters don't have emotions? Have you seen Ginti? Either they do have emotions and are in denial/misinformed, or the writers have no idea what emotionless actually means.
The show constantly makes "human emotions" a distinction from whatever it is that arbiters have. The arbiters all have really shallow, archetypal behaviors and don't display any emotions that aren't self-serving or inconsequential, while the humans shown in the series have varied, unselfish emotions and can't be pinned down to one or two anime stereotypes. Which is why the cross on Decim's eye disappeared at the end - because his emotions were backed by human empathy and weren't selfish or shallow.
Don't confuse Lack of Empathy with lack of emotions. They still act like people because they are people. Jaded, bored, and incredibly Flat people, but people nonetheless. Nona has plans and acts upon them (and I know first hand that people without emotions don't have the drive to act on anything on their own). Ginti has a bad temper (another thing that emotionless people would lack). Quin has a love of alcohol, ect. The only one who acts even remotely like an emotionless person would is, ironically, Decim.
I am not confusing the two, I'm simply stating that there is an in-verse differentiation between "human emotions" and the behaviors exhibited by the arbiters. There is a very obvious difference between the way they act and it is highlighted upo pretty often. And any time a character talks about it they clearly state "human emotions" and not just "emotions." At the end, Nona calls Decim "an arbiter with human emotions" rather than simply calling him "an arbiter with emotions," making it clear that arbiters are not necessarily completely emotionless, just that they go about things differently.
I think it has to do with what was stated in the last episode — the Arbiters are built from bits of the souls of people sent to The Void. The "life energy" has to come from somewhere, so why not from the dregs that are already judged to be unworthy? Obviously they've taken time to try and avoid adding any emotions when possible, but I don't think you can remove emotions from a soul completely, which is why we have the attitudes that the Arbiters display.
So are people who are sent to the void still able to reincarnate eventually or have any hope of getting out sometime? An unending nothingness of death makes no sense in a fictional world that has reincarnation as the whole point of reincarnation is being stripped of your former identity and transmuted back into the world. It is especially senseless if it gets determined by a game that was rigged to start with and people who don't deserve it can easily fall into that fate (Episode 4's insanely cruel ending comes to mind).
It's stated that souls cast into the void are simply lost forever, eternally floating consumed by their negative emotions. But sometimes, they are used to create more arbiters. That's it. And of course, that's the whole point of the show, that the system is unfair, the games are rigged and the arbiter's decision is, well...arbitrary. The fact that they have reincarnation in the show means nothing since their definition of the concept seems to simply be 'another chance to live' without the spiritual intrincacies of our concept of reincarnation. For them, humans are just "good" or "bad" and they either deserve to go back into the world or need to be thrown away like trash. The system is fatally flawed and Nona's plan and the Black Haired Woman's introduction to the staff is done precisely to change that.
Are new souls created? If not, when souls go into the void, it would create a net negative of souls in the universe. Also, how would the rapidly increasing world population fit into this worldvie? Is this specific to Japan, where there is isn't much increasing of population? (But that would imply the sending of souls into the void are effecting birth rates.
Is there any reason an Arbiter couldn't send everyone to be reincarnated, or to the void, as they chose? There don't seem to be any consequences to them regarding their judgements, and there don't seem to be any criteria (none made explicit to the audience, anyway) for sending people to the void or to be reincarnated, outside of the Arbiter's whim.
If the Arbiter system is clearly broken, why do they even try to fix it in the first place? Wouldn't it be more practical for whoever designed the afterlife to create a better system?
