Slavik

Because like, outside of one Magilith which takes us to the Magi Era (which can be excused because the Magi can presumably time travel, and maybe that Magilith is special), we can only visit 3 Eras from within a 100 year timeframe, and we know in the Past Era, Ceres is a young child, and while technically we don’t know if she time travelled here or is actually 100+, we know she’s living in the Future Era and spends her time there. And presumably she was around in the Present Era too, even if we don’t see it

Not only that, but no one knew the Magiliths could allow time travel until the events of the game, implying they normally don’t do that, and like Menos says, they don’t serve any known function. And after the events of the game, Menos and Velvet don’t use the Magiliths to return to either of their times, despite knowing where they are. And yeah they don’t have the controller we got, but they managed to travel without it before, so more likely they weren’t able to get the Magiliths working, which means they’re stuck in this pre-Past Era. Now that Ceres and Kuro are gone, the Magiliths no longer work

I don't know how fully accurate the idea that Ceres controls the magilith function is or at least if its the only factor. I think there is definitely some evidence to support it, such as how Ceres always appears the next time you access a magilith after obtaining a fragment of the key, which to me suggests she has a connection to the space or state you go into during time travel and can feel the magilith at least being triggered. That being said, I also think there's limits to this. If Ceres existence in that era is what is necessary for magiliths to work(not her actively being there just, that she was there at any point) then we should theoretically be able to travel to more than just 3 main points in these era, 3 main points that are slowly themselves shifting forward in time. To explain that - everytime we travel to a certain era if we change anything in it we can't go back in time to unchange it, and in fact the group cannot choose the time they go to at all. After the great disaster is triggered by Kuro, Ceres reveals that magiliths are designed to prevent paradoxes, by limiting where in time the users can go by shifting the available time point forward. You'd also mentioned that the Magi have a magilith, and i think that's important to note, because in game the magi isle npcs mention magiliths not yet being finalized, meaning our special magilith might not have worked for the magi and only worked for us which would support the Ceres/Kuro necessity theory, or is the first ever magilith prototype put into function, hence, why it only has one pathway. The function of the magilith may also depend on the loop, as it is possible that when the first time the loop ever happened, Ceres didn't exist yet but magiliths evidently did. Whether they worked though, is uncertain. You could say they worked due to the presence of Kuro, but after the finale as we've collectively figured out, Kuro returns to Fina and they aren't able to use the magiliths either even with the controller, which once again might support the Ceres necessity theory.

Another thing that i can't really wrap my head around is why Ceres can't collect the key fragments herself. She can rip portals through time just fine, so what's stopping her from just getting everything she needs? Or why doesn't she as an adult ho back in time and prevent Giro from killing her parents?

Now here's where my theory comes in: the magiliths are connected to the project(ik yawn lame, this again, its always the project but its a bit different this time) but it's not what makes them function. The magiliths came before the project and were likely part of building blocks of the project, like possibly how the magi made the project connected to the fabric of time. The magiliths when broken have some sort of white spirit inside, which is what's powering them, and magiliths create tunnels through time fabric and are responsive to the actions of time travelers, preventing them from causing too many paradoxes. In their normal state, they can take a traveler anywhere after the time of their construction. However, the project hijacks them in order to control the loop, restricting them to 3 points and a 4th special one. It also heavily restricts or fully prevents Ceres from time traveling - yes she can open time portals but we never see her step through them, at least i dont rememberan instance of it before shes to her full strength. She stays firmly in the future era, and the only other times we see her, she's the age she would appropriately be in that era. She's only able to rip portals through time because, like the project, she's connected to time fabric itself. I think evidence for this is that at the end the cast ends up in the pre past era, somewhere you can't go by magilith, somewhere only a Ceres at full strength hijacking the project can send you to.

The reason that Kuro and the rest can't time travel is for two reasons then: the era they end up in is outside of the acceptable 3 points, so the magiliths are just straight up locked. This is why Menos doesn't think the magiliths do anything- They only become functional in certain time interval or after a certain point in the era. Kuro maybe would've been able to override this but he's now defective - the project understands him to be hostile to it, probably restricting him too, and since Ceres is no longer around to make the controller force activate the magiliths, he's trapped, and so is everyone else

First im gonna put my pieces of evidence:

1) Our first introduction to Kuro, the opening scene, which we later learn to be the magi testing whether their special force agent(? Don't know what to call it, but he's a special guy) is operational. The scene itself has implications, like Kuro needing to be instructed to walk, and look, but what interests me the most is how the cutscene ends. The sound effect that is played in the white screen is that of the cannon used to launch things into the anomaly. Not the magilith, the cannon. This is important because it established that Giro didn't get to the future using a magilith. Another important detail is what the researchers say - they say that because he is perfect, they will be able to activate the machine. The machine theyre talking about is the project, multiple MRC npcs basically confirm this with dialogue like "were counting on you for the project to survive", but important to note that by the point of Giro getting shot into the anomaly the project wasnt even close to completion- in game when we as Kuro go (or return) to the MRC an npc researcher says "you're already back?" Like very little time has passed since they sent him away, and we can learn the project is less than 50% complete(the guy who's playthrough im watching to see this doesn’t dialogue the robots sadly so I can't confirm exact dialogue, cuz I can't access the game itself rn)

2) Project being in the anomaly. There is also only one project MRC npcs also give more evidence for the loop being mirror like instead of hard reset, as they say the fished the stone of time out of the anomaly, and it can only end up there after the Ceres fight, which, another important detail to note, this means that no one leaving the project post end boss fight took the stone.

3) Giro knows about Ceres, is hunting her, and attempts to drain her of her power. Magi do not mention any specific threats to the project. Giro also has to find some way to get to the empire era

4) end cutscene of fina pressing buttons to reveal and entering Kuro that she runs to. It could be possible those buttons do something but the game implies them to be useless.

So, what does all this indicate.

We clearly know Giro/Kuro to be a clone, or otherwise mind wiped candidate that applied to be part of the MRC project. The magi had made the project to prevent the end of time, which they believed would be caused once the anomaly swallowed the world whole, so they made The Project, a machine that warps reality and bends time to by, uncertain means, do something to the anomaly (prevent it from expanding?), but it obviously can't manage itself, so Giro was chosen to man the project, from the inside of the anomaly, and was sent there to prepare for its arrival.

But my understanding is that final cutscene with Fina in the Laboratory up to Ceres portalling him is Giro, and then everything after, up to the Ceres boss battle is Kuro, yeah? And that Kuro's existence only comes about via the time loop (which would tie him in with Ceres, who shares that feature (maybe that could also explain why she can't erase him? Because he's tied to the Project via this like her?))

Though I'm pretty sure I understand some of the details wrong

Okay I can understand some of this logic. For one, it can explain how Sid confused Giro with Kuro in his backstory, because they were one and the same, and like I said, possibly explains Kuro and Ceres' intrinsic connection. And maybe also the Project being involved in the "creation" of Kuro could explain why he looks like a teenager when Giro probably wasn't, maybe he got "reset" back to how he was supposed to be when he first time travelled to the Past Era

Though I do question why Giro and Fina would have gotten together, because again, Sid exists. Was Giro just like "alright I guess you're my lab assistant" and did Fina either not recognize this wasn't Kuro, or convinced herself that helping Giro could bring back the Kuro she knew? I mean I can believe she went a bit crazy with the final few cutscenes, but I don't know

I'm also not sure why then Fina would have died/disappeared, if Giro didn't get rid of her. And also, I think in his first message he says he "disposed of the defective model, him and the woman" or something like that, something that implied there were two people, the "defective model" likely being Kuro

And also, there's something up with Giro and Ceres, but I can't quite put my finger on it. You're correct about the fact that the Molecular Research Center people never mention Ceres, and yet Giro knows of her, and seems to have specifically come to this era to deal with her. Is that what you mean when you're talking about how the Project would've changed Giro? Like sometime in between when he was first sent on his mission and when he first comes to the Laboratory, he learns about Ceres and makes it his mission to get rid of her, presumable through her tampering with the Project?

So then with that logic, the timeline we're first given to understand makes more sense; G was sent back to help with the Project, loses his memory and becomes Kuro, but then by the end of the game, his dealings with Ceres and the Project somehow bring back to him his original goal and he becomes Professor Giro when he meets back with Fina again?

I don't know, like I said, this is all so very confusing

But back to that bit about Giro and Ceres being strange, I want to point out that from what I understand, his intent was to destroy her, and when he couldn't, he made the Weapon as a way to weaken her, so the Weapon wasn't part of the original plan (which fittingly would make it an "Anomaly"). But also, I think in the final log (which I don't have saved) he says he plans on letting her out of the device and questioning her, which implies to me that he doesn't really understand what exactly Ceres' role in all of this is, and also that the Weapon, which Kuro is programmed to fire, was never part of the plan

Now that you've pointed out Giros first message, it's all a lot more clear that i made a mistake and where. Kuro does return from the void to Fina, that IS Kuro in the final cutscene. Giros first message directly states that he did away with both Kuro AND Fina. When he says he arrived to this time period and tracked the defective model, that's how he found the lab! Thank you, I'd completely missed that, this changes everything!

I've made some graphs to illustrate my new theory

It was Kuro in that cutscene, and Sid is Kuros and Finas kid. In Giros lab there is writing on the walls that is clearly not by Giro, which details attempt to "return to our time" which is most likely by Fina, since "our" could not describe just Kuro. They were stuck in the past, so they were bracing for Giro, but, he. Desposed of them both.

So actually Fina never got with Giro, only with Kuro, and they disappeared because Giro likely killed them both. Also, I completely forgot about Giros messages, so yes he did mean to destroy her but couldn't, likely because as you said, she's also linked to the project, or as I believe she's linked somehow to Tiki, the time guardian. This is based on the fact, as you said, Giro decides to question her, he's starved for information. Means the project doesn't know everything which is weird, if she's directly linked. Giro/Kuro are tied to Ceres in a roundabout frustratingly vague way, but by my theory Giro/Kuro are tied to the project because they are designed to manage it - the captain of the project, basically. Hence, why Ceres can't erase him(or more specifically teleport him away, none of the characters actually seemed to have been erased just, transported into an identical room or into the same room in the future, post battle), project literally cannot do that, as it can't override the guy with admin privilege.

So, basically. At the final boss Ceres battle, she reveals to Kuro he's in a loop. He becomes defective, abandons his mission, but (electronic implants? Tracker?) Shows his location. This is why the project sends Giro to the same timeline - it needs to replace the defective captain/acting hand of itself with a working one, so he can deal with the Ceres threat. Giro arrives from the future, kills both Kuro and Fina, waits until Ceres is born, Desposes of Menos and Velvet, kidnaps her, attempts to destroy her, can't, makes the weapon instead, gets amnesiaced and turned into Kuro, game events happen, final battle with Ceres aaannnd cycle begins again. So I guess you could say the final boss battle is a point where a new loop starts?