The best guess at the moment is Pareidolia. Neither HOPE nor Wires profit from changing things, since the cycles already changed from one to the other for hundreds of years. Following that logic, Himawari should have been working under Pareidolia until saving Ayane.
However, there are four users, not three. So a very strong possibility exists that Himawari's goals aligned with Pareidolia's up to a certain point. But they're not necessarily the same endgoal, and she may be working under USER4 instead. Both of them needed Akira to remember his past, and possibly for Maya to be taken out. Did both of them need Sekai to be brought back, instead of just Akira remembering her? unknown.
Who are the ones that sent Nao-chan to help? It's around that time that things start to get really messy, because it's around the point that Akira is first saved from factory reset by an unknown entity - other than USER1 and USER2 (during "untitled") that the status quo crumbles. It isn't about HOPE versus Wires anymore. Pareidolia makes itself known, and other entities start appearing. So from that point forward, it's also acceptable for HOPE and Wires to start trying to change things too (to restore the old status quo if nothing else).
So we're at a point in the story that every entity has cause for trying to interfere. Which makes it narrowing down that much harder (this may include random gods and the world itself).
Pareidolia does seem to have a good motive to have caused the sinkhole, since he probably needed Akira to start recovering some memories of Sekai before her restoration was possible. On the other hand, I question whether he has the power to cause something like that. Especially since it happens right after Wires's reset, so Pareidolia shouldn't be in control of the Terminal. From what we've seen, the powers of the gods seem to be about affecting people mentally, with some limited ability to reset time, rather than large-scale physical changes.
Another possibility is that it was caused by the World Itself, which might have the power and seems to be at least partially in league with Pareidolia. But that probably only makes sense if the World Itself is distinct from Sekai.
I personally like the idea that the sinkhole was caused by Kumon-mi itself. The city is described as a living, evolving thing and it even "moves" (as Yasu says in Pareidolia's Halloween). It seems to have some underlying purpose to it that we still don't know, but it's likely connected to the resets and so might have something to do with fixing its broken inhabitants. Of course that still leaves the open question of why the sinkhole only happened in this cycle, for which I don't have an explanation.
Yes, Akira calls 79/You did it "Long Maya", that's who I meant. The four known Maya freelancers are:
1. 61 6d 20 69 20 6f 6b 61 79/am i okay (shows up again during this update, and showed up constantly in the beginning of the game).
2. 79 6f 75 64 69 64 69 74/you did it/Long Maya (host of all the interviews, seemed to intend to factory reset Akira during "untitled").
3. Moyo (eats cockroaches).
4.
Possibly Shadow Maya.
The reason we call them freelancers is because they change camps and have been seen working for multiple gods (this is an interpretation). Their canonical title is "children of the clockwork", since that's what Long Maya calls herself and Moyo to distinguish them from our Maya (Prime). Long Maya seemed to be working for HOPE during the event that she collects his semen (it takes place inside the church of New HOPE), "untitled" also seemed to be aligned with HOPE. I'd like to know why you associate Long Maya with Wires.
It's definitely possible.
Edit: Added images.
AmIOkay isn't in the scene ("Good Boy") where Long Maya mentions the fourth. The three that are present are Long Maya, Moyo, and "Chair" (who has never said anything). So it's possible that AmIOkay is the fourth, though I think probably not. She's also not present when Long Maya talks about "children of the clockwork" so we don't know if that includes her.
I strongly suspect there are multiple versions of AmIOkay, given how differently she acts in different scenes (or even in the same events, like "The Room with Clocks"). There might just be two of them, as one version of her refers to "The other me. The better one." (I think in "How I Feel"), which could be a different AmIOkay or could just be the "real" Maya. Personally I'm a fan of the idea that each time Maya has been reset, the old consciousness lives on as a new version of AmIOkay. Maybe the longer they've been stuck wherever they are (the wishing well and/or the bottom of everything or something), the less human they become.
Wakana definitely treats her as if she was a plague, a larger than life contaminant. And I see the appeal of Sekai being this absolute evil, a true malevolent person that simply is (which definitely exists to some degree). However, there are two points to this.
I think we can probably trust the "memories" that the Xoanon shows us in "Mother's Milk", since its role is to be an observer and cataloguer of true experiences. From those we know that Sekai definitely abused him and was the one who initiated it, but apparently also loved him in some sort of twisted way.
I agree the rest of what we know is unreliable. In particular, I think it's possible and maybe even likely that the Sekai in Akira's head is Pareidolia creating a fictional version of Sekai using some amount of the real one taken from Akira's memories. Pareidolia likes to pretend to be others (the other gods, a narrator) and it fits with his name: we/Akira perceive human features (e.g. Sekai) emerging from something inhuman (e.g. a god/user/voice or whatever).
At no point during her first events for this update Akira gave her the idea he wanted to have sex with her. In fact, he tries to leave multiple times. The whole conversation was about her forcing her points on him. When she offers sex, it's a direct response to believing that it's the only way to keep him with her. And that if he refuses, it means he's going to leave her. She's not
letting it happen, she's counting on it happening because in her mind it's the way things
have to go for him to remain with her. But that's
her idea, not Akira's.
Now, we're all adults, and from the reaction to the event, I think it's safe to say most of us understand that Io's out of her mind. The correct decision is not to engage in her damaged view of the situation, and to prove to her through actions that there is a third way. That way is not having sex with her and proceed to not abandoning her regardless. But we're not talking about how we view the situation, we're talking about how Io does.
I don't even see where we diverge so much in our take of the situation, because you basically explained exactly why she thinks this is a transaction but concluded by saying it's not a transaction. "I was already trash, and this person now knows the part of me I most despise, and didn't want him to find out. The only thing he's interested in is sex, that's the one thing I have left to give. Let's get it over with, this is the only path forward for him to stay with me, and for some reason, I can't bear not having him." That's her logic, it's her last resort transaction.
I think I understand your perspective, but I don't think that I agree with it. I think the talk of a transaction is for Akira's benefit, trying to justify Io's irrational actions. Maybe there's an element of trying to convince herself as well, but I don't think she truly believes it. Instead she's acting out of learned helplessness, as a victim of repeated abuse who has resigned herself to her fate. She's decided that she's a tool to be used, and he's an abuser just like her mother and will eventually get what he wants, so she might as well give in and get it over with.
If this was really about a transaction, she wouldn't be choosing to make the offer at the very point where she is most disgusted by Akira and his "love". Prior to this event, she was excited about Uta having sex with Akira as her proxy. Now she'd rather keep him
away from Uta. She views him as an animal acting only on instinct. She has to try to tell herself that "maybe he's not so bad" once he starts raping her (verbal consent or no, she clearly doesn't want it). And if she was really so concerned with keeping him in her life, she wouldn't be kicking him out and indefinitely ghosting him after it's over.
Edit: I don't think Io was talking about her father killing himself and her mother. The "maybe he's killed them both" seems like it's referring to God.