We won't know where this takes place in the timeline until the end of the series

While it's stated to be a sequel (set 25 years after the series) some things don't seem to match up or make too much sense yet. Perhaps this is because it's not a sequel at all.

It might take place:

  • After the first series, which is the truth as far as we know right now.
  • Before the original. Certain things like Noah's name due to the knowledge we learn of Earth in the original series and Identical Grandson looking characters, plus the mysterious nature of Nirvash and the Scub Coral can lead to this.
  • In the Alternate Universe from the movie. No reason for this yet, just a guess.
    • Explained in the recap/prologue. Apparently, Eureka has to gather seven fragments scattered in another universe to prevent the end of the world. Unfortunately, she has to leave Renton behind...
      • I've heard that that was a non-canon recap episode.

Eureka Seven is Alternate History or future history

It was noted that Okinawa was independent of Japan by 2025. Either Okinawa seceded by the 2020s or Okinawa while as a US occupied territory in the 1940s-60s was given independence instead of being retroceded to Japan.

Time Travel explains everything

Skub is explicitly stated to have first appeared in 1940. The Earth's landmass is clearly visible and uncovered, which does not jive at all with the setting of E7. explanation: due to Weird Plot Shit, a time portal opened up, depositing skub coral all across 1940's earth with more portals opening periodically, such as one that dropped Eureka and baby Ao on 2010-ish Okinawa with the Nirvash.

  • Knock a few centuries off that number. Secrets were around in the 1700s.

Eureka was sent to the past

Its obvious this isn't the original timeline given how in it, they didn't even KNOW they were on Earth. So Eureka, somehow, was sent to the past before things.

  • The only problem with this theory is that they know about trapars and how to use them. They also have flying cars and huge mecha.
    • See the theory above this. Scub has apparently been dropping in unannounced for over 80 years by the time of AO, so its entirely possible that humanity got a jump-start on trapar science. As for IF Os, they seem to be fairly rare (Ao and Gazelle's smugglers mistook the Nirvash for some sort of flying tank at first, rather than a mech) and the Nirvash seems to have been used for scientific research, so its not impossible that IF Os were reverse-enginnered from the Nirvash around the time Eureka was thrown onto Okinawa.

AO isn't in the real world

It's instead following the people who disappeared into the Scub Coral mindspace at the end of E7. Hence the Scub coral/G monsters teleporting in are from the 'real world', while the world itself is built from the memories of the coral from its early days, plus reflected aspects of the real world. (Hence the appearance of expys of the characters in the first series. Pied Piper for example are reflections of the Ageha Squad, who are remembered as heroes by the transferees, and so actually are heroes here.) 'Astral' Ocean is a reference to astral projection or astral body.

It's 2025... years after Eureka 7

We know that Eureka's brethren Sakuya did not age at all in 40 years. This means that Eureka, despite being young-adult in terms of apparent age, could have been around for faaar longer than that. Long enough for Renton to have died long ago, for everyone to have forgotten about LF Os and for the state of the world to have changed to the way it is now.

  • Doesn't explain Nirvash though, and Word of God confirming Ao to be Renton's son.

Something terrible happened to Renton

Renton wouldn't abandon Eureka and Ao over anything. We know this. However, he has yet to be mentioned and he hasn't even been seen in flashbacks. The only explanation is that he was kidnapped for some reason by something, or killed. Or perhaps it's a problem with the scub. In any case, there's something stopping him from getting back to his family, something even he can't overcome (at least without Eureka and/or Ao's help).

Counter WMG: Something terrible happened to Eureka

Which is why she ended up there in the first place. Renton will show up in a later episode looking for them.

  • Confirmed in the recap/prologue. Eureka has to gather seven fragments scattered in another universe to prevent the end of the world. She has to leave everyone she knows behind, but Renton promises to find her one way or another.
    • We don't yet know if that's canon, but many fans are already doubting it and Word of God has yet to say anything.

Gazelle is Holland and Talho's son

Not hard to believe.

  • Unless they alter that for the anime, we've seen his dad in the manga. He looks a lot like Charles Beams.
    • His dad was seen in the manga? Also, Charles couldn't have a kid with Ray because she was sterile. However, seeing as how the original series and the manga differed, it's not hard to believe the same might be true for this one.
      • Differed on minor points, not the big ones. Gazelle is revealed to be related to that guy that kidnapped Ao at the beginning of chapter 3. The thing about him looking like Beams wasn't meant to imply he actually is Beams.

The series takes place in the confirmed split universe of the original series.

At the end of the first series, Nirvash, becoming the Coralian head, took half of the Earth's population to an other universe. Perhaps Eureka was dragged across to it through the actions of the Scub. Evidence here and here but be warned - they contain spoilers to the end of Eureka Seven.

Only children can pilot IFO's because the IFO's themselves want it that way.

IFO's are said to have been reverse engineered from the original Nirvash, which was the only somewhat-sentient/intelligent LFO in the original series (barring theEND due to it's origins). Because of this, they can choose who they will start up for. With AO's message of not allowing the youth to follow in the footsteps and mistakes of the previous generation, they don't allow any "adults" to pilot them - only children are ideallic and fair enough for the IFO's to want to work.

Another point to their intelligence was revealed in a flashback in episode 3. Eureka is shown familirizing the neo-Nirvash's key/bracelet so that it remembers Ao and allows him to pilot. It works.

The series takes place after Instrumentality

This is why there are so many differences from the original series (no graffiti on the moon, no Renton, etc.) - after Instrumentality the Eureka Seven world rebuilt itself by "rebooting" to a different point in time based on Eureka's (or the Scub's) memory.

Also, this WMG was bound to happen eventually.

Fleur's mother is Maeter from the first series

We know who her dad is, but not her mother. The only problem with this is if AO actually does take place in the alternate universe/dimension that the Nirvash created at the end of the original series as many fans suspect.

Elena is Moondoggie's and Gidget's daughter

She looks a lot like Gidget, and this would explain her Mukokuseki status. As with the above WMG on Maeter and Fleur, the biggest problem for this WMG would be if the series takes place in the alternate universe/dimension that the Nirvash created at the end of the original series like many fans are suspecting.

Elena is Anemone's descendant

Mostly going with her hair colour and affinity for massive firepower on this one.

Generation Bleu will end up as antagonists

While the Pied Piper crew seem benign, the President clearly has some kind of an agenda from his meeting with Gazella and company. Not much to go on besides that right now, but I am highly suspicious.

Truth is...

A Secret in human form. This would make him pretty much the anti-Eureka; where she was a Coralian-created human sent to understand humanity, Truth is a Secret in human-form, sent to destroy the Scub (and humans).

His powers (the blue energy attack was like that of a previous Secret) and clothes while he isn't shapeshifting give it away.

The item buried under Generation Bleu's base somehow regenerated itself when it entered AO's timeline/time period/universe.

That or it's an Alternate Universe version of type TheEND that wasn't destroyed.