Ok I did a quick summary of EXTELLA/Zero from nasu's diary

This is basically an alternate reconstruction of Extra and serves as the base for EXTELLA, so basically EXTELLA takes place after this retelling. It consits of only one route. nasu planned to release as a book or something of this but he decided to just post the general outline of it on his diary ;

>Main Character:
Kishinami Hakuno (Male)
Basically everything is the same as PSP version

>Saber (Nero)
Same as PSP version

>Female Classmate (Female MC):
A girl who happens to pass by from time to time when Hakuno is in trouble to give him advice.
She is always eating yakisoba pan.
She's a character that wasn't in the PSP version so mislead the users by having them think "a new heroine!?"

--> Reveal
Isotope of Hakuno.
A NPC created by the SE.RA.PH, modeled after Hakuno. However since they are the same existence, and thus contradict each other, she has been arranged to be a female version of him.
When Hakuno aqcuires his ego, she also does since they are linked.
(However unlike male hakuno, she has no soul since there is only one soul)
She quickly recognizes she is not regular.
Since she is an inferior copy, she cannot bear the burden of the ego (soul) and is fated to self-destruct.
(Even if she wins the 7th round she will disappear right after, but archer is the only one who realizes this)

>Archer (Nameless):
Female MC's servant. Since he was summoned by the female MC, who has no soul, he is also not summoned in his regular form.
Half his body is collapsed, and burned.
Though he knows the circumstances of female MC, he lends her his strength and helps her fight until the very end.
--> From time to time, Archer will also help out hakuno which serves as foreshadowing. As for why he helps out hakuno, it is because if hakuno dies, so will female MC.
Archer is aiming for a "though he couldn't bring her to full victory and she didn't survive, she was satisfied"-ending.
-->Since his body is half-destroyed, Nero and Tamamo don't recognize who he is in EXTELLA.
The Archer in EXTELLA is from a world where the female MC won.

>Rin & Rani:
A little less screen-time than in the PSP ver, but mostly the same roles

Leo:
Mostly the same as in the PSP ver, but he loses the sixth round.
-->foreshadowing
He shows interest in hakuno and talks to him many times, but his conversations always seem incoherent.
"Huh? Didn't we talk about this before?"
"Yes, I am interested in you as well"
It's because Leo has been interacting with the female MC also.
He loses against female MC in the sixth round.

>Saber (Gawain)
It's Gawain.

>Julius & Li:
Mostly the same

>Shinji & Drake:
The same.


>Atlam:
Fourth round opponent. His servant is Caster (tamamo).
New master for the EXTRA reconstruction for the sake of EXTELLA.
Is acquainted with Leo in the real world. Because of the oil situation in EXTRA-world he's slightly uncomposed, but his personality is mostly the same.
Claims he's a feminist but only sees women as tools.
Says he respects Caster but looks down on her.
In the fourth round, he orders caster to seduce hakuno and make him feel sorry for her.
After he sends caster off he accesses the earth for data on hakuno, but finds nothing and is bewildered.
When he loses the battle against hakuno, he uses tamamo as a scapegoat to escape and survive on his own, but he isdisposed of by either julius or the moon cell.

>Caster (tamamo)
Atlam's servant.
Knows she is being used, but won't object since a servant is supposed to obey until the end. (of course if atlam cancels their contract things are different)
After the battle she is sacrificed by atlam and burns out.
MC uses a command seal to help her.
Caster recovers quickly "Finally, I'm free!"
This is like when Arc easily escaped being erased by the firewall.
After this she starts calling herself hakuno's servant.

>Dan & Archer:
Same.

>Twice Pieceman:
Mostly the same, but try to have him appear more so it's not so sudden at the end.

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>PART II

>Reconstruction
It's a short version so it will only touch upon the important parts and cut all excess.
However, to be mentioned is that this is just if it was the nero route. If it's Archer or Tamamo route the details will differ.

>1st round
Mostly the same.
If there's budget, make the "next opponent announcement" flashier.

>2nd Round
same

>3rd round
same.
at the end caster & atlam are announced as the next opponents.

>4th round
Atlam is a character even more connected to the earth than leo, so explain the worldview through him. What's going on on the surface, how has the world ended in 2030.
Atlam feigns to be a virtuos person and tells hakuno he should "lose in order to let me live to save the world".
After the battle caster joins and nero and caster start happily fighting.
This changes their realtionship from "two heroines in different worlds" to "two heroines in one world"

>5th round
Same

>Interlude
CCC happens around here. Caster remembers but Nero hardly does. "I feel like i fought a life-long roval called elizabeth, but what round was that again?"

>6th~7th round
Rin and Rani are defeated and they say their farewells.
Finally it's time to face Leo... is what Hakuno thinks but he finds out Leo's lost.

The name of the master who defeated Leo and made it to the 7th round is hidden by jamming, and there's no trace of a master. Tamamo and Nero try to find out who it is but they find no one and cannot remove the mozaic from the name.
One of them proposes the idea that "maybe it's not hidden, but it was like this from the beginning?" and they come to the conclusion that their opponent has no name.

They protest to father kotomine that this is irregular, but he tells them that "no, your fight is in a sense very fair". Not knowing who his opponent is, hakuno steps into the elevator. At his side is noone.

Once he reaches the battlefield, there's a wasteland like the grand canyon.
Both Hakuno and Female MC appear
His opponent was the female classmate. "Ah, I thought so..." Hakuno says contentedly.
Girl: "Let's go Archer. This is my last fight"
Appearing at the call of the girl's voice, Archer flies at Nero
The girl removes the texture she put over her avatar, to reveal her true face.
Her long hair swept by the wind, there stand the female MC, dignified.

Here we see things from her perspective a little.
We see how she struggled through the war, just like hakuno.
Her 6th round is the same as the PSP version 7th round.
->To leo, even if it was against the female MC, it doesn't change the fact that he lost to "Hakuno"

7th round end. The girl disappears together with Archer.
The male MC inherits the memories of female MC's confrontation with Leo.

>On the way to the moon cell core
On the way there they get caught by a bug check.
moon cell gets HELLA MAD(nasu's own words) that a servant who's supposed to already have lost is there (Tamamo).
--> parting with caster. imagine their parting scene in CCC. Unlike CC however, this check isn't so strong that she is deleted.
Caster plans to gain points with the MC by risking her life to have a heartfelt farewell scene, but Nero sees through her tricks. "Whatever, try again later!" "I'LL BE BAAAAAAAAAAAAAAAAAAAAAAAAAAAACK!"
That sure was a terrible accident, say hakuno as thei finally arrive to face twice.

>Messiah
Twice talks a lot

After Twice is defeated, take the end of the PSP ver and add CCC Nero end to it and have it kind of connect to EXTELLA like that.