This Prologue reminds me of the movie Avatar. I don't know why. Nice work so far.

Thumbs up.

Nooo! That's such a horrible cliffhanger! I want to know they're safe from the Sons! (Tangent: They (the Sons) really need to be fully exterminated.)
Go, Hanatarou! He took a level in badass, between the pesquisa and kind-of fighting. Though, I don't understand his reasoning for not bringing up the pesquisa issue; them knowing the problem and learning to use it "properly" would keep everyone safer, so it's not pointless.
Somehow, I didn't connect the Eaters with Aaroniero until you mentioned him in this chapter's A/N. That makes all of them, right?
I want more! This is past the halfway point, right? The mystery of the past is almost filled in, the mystery of the first expedition is solved, and now they just have to find Rukia... and turn her back and/or convince her to come home (and she'll probably have to deal with that whole "which place is my home/which life do I choose?" dilemma)... Oh, damn, I hope the inter-society standoff is only going to be delved into enough to connect the main characters with each other. Otherwise, it'll just be in the way, holding up what I want to see.

Ulquiorra calls Orihime "woman," not "little girl."
Yay, flashbacks and answers!
Well, that's an interesting thought; I think you're right about how American politicians and/or military would handle learning of a new realm.
So, it's Urahara's fault Yamamoto died and stuff got worse in Soul Society.

Is that slave girl Lyanna or whatever her name was from the auction?
I was wondering if Zommari Lereaux and Aaroniero had religions and who the Others were. Well, now I know there's a seventh, at least. I briefly thought the "False Sun" was Aizen, but apparently it was Zommari.
Well, duh, Isra is Rukia. Now, though, we know that she has a different personality because she pulled a metaphorical Aang to escape the inner Hollow trying to consume her. I wonder if using her fake resurreccion accelerated the process? We also now know that the rest of the team all succumbed and one met Edwyn.

"As the name suggested, Sanction was built first as a sanctuary for the Daughters of the Sand. But it was found to be inadequate by the later Queens. So the Triples had spent subsequent generations to make their city not only as strong but as beautiful as themselves." This is in the first paragraph and then soon after is repeated as its own paragraph. I think it fits better in the second place but well enough in the first. Either way, though, it should only be in one place.

So much character development! That was great.
"Epic-length": *looks at 23,000 average word count* I can definitely see that.
This definitely has been taking the slow route compared to my usual reading. It's been mentally taxing (to my shame) to read this due to the lack of action and I've had to tackle it in chunks, but it's been intriguing enough that I didn't get bored with it despite my unpreparedness for it. I think you're right about your storytelling approach and are succeeding in your endeavor. As for threads, I did notice at a few points how the paths of certain independently followed minor characters whom I can't remember at the moment crossed with each other's or those of the main protagonists. Oh, wait, one example was the Octavian(?) ruin in Las Noches where Nelliel raged and then Tatsuki and Nemu were there later.

It seems strange that they keep finding people who are able and willing to provide such complete accounts of the next step of the first expedition's journey and useful information to figuring out what was going on. Still, the justifications so far have been believable. At any rate, I'm curious about who the Others are, now. Also, how are they planning to find Nemu, and will she have joined the revelry as she descends into arrancarhood? Speaking of which, I hope Tatsuki's going to mention the inner Hollow problem soon. Maybe Ikkaku will bring it up, considering he noticed something was wrong?

Uh-oh, they're gaining Arrancar instincts... Also, I had thought of it based on the inversion of her hair's appearance, but now there's support for the idea that Rukia has either become an "inner shinigami" to the arrancar self that developed and took over or developed a split-personality that has become the dominant personality.
Yay, more information. Probably, entries four through 16 were about discoveries in Octavia and were erased by somebody from there, though why he or she would then let the expedition members go is another question.
How do they know where they are on the map such that they can say Pantera is slightly northwest of where they are?

SHE'S FREAKING KARIN?! O.O WHAT?!
Hoooly crap. Well, that's new context for Hitsugaya's interest in her... Also, you did a better job of keeping it subtle this time, I think.
Now I really want to know what Ichigo did wrong on the Karakura apocalypse day (I think that's what everyone's talking about).

Well, well. So, basically the various arrancar societies are running the gamut as substitutes for the ways human society can be up. After looking them up, the religions don't seem to be related to each espada's aspect of death, so from that and other evidence the religions must be based on their personalities. Why does each espada have a society (and most have a religion), though?

"...listen to them and try your best to get more information and try your best to get more information." Obviously, that long string was pasted twice and one should be removed. I've been leaving the spelling/grammar stuff alone because I've already mentioned it, but that one earned special recognition.

Well, that was really up. I skimmed past most of the mutilation part, but I still felt nauseous thinking about it afterward. ...Wait, why would Nnoitra have a religion when he died before the first war was over?
The idea that Urahara smuggled and somehow implemented trains and other technology and goods into Las Noches is hilarious.
Okay, we learned a lot more about what happened. This is good. Also, if it weren't for the fact I would probably have the same reaction (minus the nosebleed), I would be upset at Hanatarou. Then again, if you hadn't shown her innocent reaction I would have suspected she'd just failed to lure him into a trap.
Sooo, at least part of the change is that Kenpachi didn't kill Tesla, and that's why Nnoitra has a religion?

I hope Nemu hears from Ikkaku or Tatsuki than Yachiru was trying to find her.

"Ichigo saw Rangiku leaning against the wall next to the doubt." Hahaha. Do you mean the door?
"Most of all, I feel proud of you in the quiet moments in the quiet moments you spent sitting by a sick patient or..." "In the quiet moments" is there an extra time. Also, seeing as everything else is in present-tense: "spend," not spent.

So, Chad doesn't uphold his vow to never fight in defense of himself anymore? Also, Hollows are supposed to not have hearts, right? Isn't that the whole point? I mean, Arrancar can have physical hearts because they have human bodies, but for regular Hollows I thought the whole "their hearts become their masks" thing was literal.
Urahara calls Ichigo "Captain Kuchiki" at one point.
Nelliel (i.e., adult Nel) doesn't have the lisp and says Ichigo's name correctly. Also, their apparent past "friends with benefits" not-relationship is another thing where you had subtle hints and the message was understood (in this case, that the rumors about them in Soul Society are true), but then you got less subtle, like you were saying, "Hey, readers! Do you get what I'm getting at here?"

So, now we know at least where Rukia is if not what happened to her. Where are the rest of the expedition, and will Rukia be found?
Were Ichigo and Rukia together when the situation with Nelliel happened? Because I have a hard time believing Ichigo would cheat.
I don't like dystopian settings, but I'm being pulled along by the mystery; I want to know what happened in the 200-year time skip.
Also, I fogot to mention it before, but Byakuya trying to make a meaningful statement of approval to Ichigo and Ichigo missing the point was funny.

It's an interesting idea. I certainly have respect for the average word count per chapter. I'm assuming you started this before the Deicide arc or at least before it was over, seeing as Ichigo never lost his powers and the Visored weren't given their old captain positions. I liked that you were showing and not telling that the name was Renji's by context of Byakuya's familiarity with the name's owner and things they said about him, but then you went and wrote explicitly that the name was Renji's.

Mostly, the grammar is great. However, a few grammatical issues:
You've got everyone else's names in Western order, but "Hirako Shinji" is the Eastern order. I don't see why Rukia would start calling Byakuya "Nii-san" instead of "Nii-sama". In the captains' meeting hall, she calls him "Nee-" and gets cut off, but that means "sister". There are at least two to three times as many capitalized words as there should be. Finally, there are a few typos here and there, but I won't list them.

Great story. I can really see where some of your influences have come from and this is a great example of world building. Please please please continue this story whenever you can.