I decided to try translating some of this story quest because of that very interesting chap that joins us, for my own benefit. Since there are people interested in knowing why he joins us, I figured I should share my translation.
WARNING: I'm not fluent in Japanese; I'm still learning. I translated this with a huge help of a dictionary and employing what I know of Japanese grammar. There MAY be errors in this translation. If someone better at Japanese than me spots something translated incorrectly, please correct me. Also there are spots I just plain didn't understand well enough to translate. I don't have much experience either, so the TL might sound weird in English.
Starting solely from after the player and Matoi get eaten. I figure the parts before that are easy to understand based on what has been posted on this thread so far.
[spoiler-box]The first cutscene in the new area
[spoiler-box](Matoi)
[Player]...
...Where are we?
(???)
...Well well, if it isn't some
seriously nostalgic faces.
(Matoi)
That voice is...!
(Luther)
Indeed, meeting again in this
place is unexpected...
((I'm not sure how to translate the rest))
(Matoi)
...Luther!
(Luther)
Woah, would you stop that?
I didn't come to this place
to fight you.
<The player has the choices of "What is this place?" and "Why are you still alive?">
<"What is this place?" response>
(Luther)
Even without asking, surely you know?
This is inside [Double]'s stomach.
That Dark Falz's inner universe.
Both you and me got eaten, you see.
By Dark Falz [Double].
<"Why are you still alive?" response>
(Luther)
Haha, you ask a strange question.
Under these circumstances, would you
say that I'm alive?
This is [Double]'s inner universe.
Both you and me got eaten,
which means we're inside a miserable stomach.
((Not entirely sure on this.))
<After either dialogue branch>
(Luther)
Nonetheless, I'm not particularly displeased.
The experience of entering a Dark Falz
isn't something that can be had easily.
((Not sure about this either.))
If you end up getting used to it,
why, it's quite fun.
Besides, I don't have any interest in the outside anymore.
Xion is gone... I have no interest
in a world without omniscience.
Do you understand, young lady?
I no longer have a reason to oppose you.
...So, could you lower your weapon?
Thank you.
Well then, while still carrying your weapons,
I would like you to follow me.
Although there are a few dangers,
this is quite an interesting place.
I'll guide you since it's so troublesome.[/spoiler-box]
The field conversation after the first cutscene
[spoiler-box](Luther)
First off, I would like you to follow this road.
While enjoying this space, yes?
<Upon encountering the first Darkers>
(Matoi)
There are a lot of small Darkers...!
(Luther)
Yes, better be careful about those.
They embrace and self-destruct.
It's a quite amusing Darker.
<After defeating them>
(Matoi)
If there are a lot of these Darkers,
it could be troublesome...
<After defeating the oceanids at the first crossroad>
(Luther)
It's better to go north.
Because going the other way will just circle around.
Whether you trust me, I'll leave it up to you.
(Matoi)
...I wonder if there's no choice but to believe now.
<If ignoring Luther's directions>
(Luther)
Fufu, you won't trust me.
Oh well, there's no stopping that.
This is the path you chose.
The obstacles are also your responsibility.
Please crush them yourselves.
<After clearing the enemies>
(Luther)
This is leading back to the original path.
In other words, it turns out we're still advancing
towards the path I indicated... What will you do?
((I'm not entirely sure if this is how it's supposed to be translated.))
<If still ignoring Luther's directions>
(Luther)
Sigh... It's sad how, to this point, my kindness
hasn't been taken into consideration.
I already said there's no benefit in
deceiving you here.
((I don't understand what exactly he's saying afterwards,
but it's something about being unable to change their minds, I think.))
<After defeating the enemies>
(Luther)
It seems like you've defeated everything here.
Shall we move on?
((At the next crossroad, rabbit toy darkers spawn and Luther explains them. Too lazy to translate that though.))
(Luther)
You should go towards that light.
We'll probably find more interesting things.
<If Luther's directions are ignored>
((I don't remember the context of this, so I can't translate properly.
But Luther comments that they're even more stubborn than expected.))
<Once insect darkers spawn while ignoring Luther's directions>
(Luther)
[Apprentice]'s Darkers are increasing.
In that case, up ahead is...
<Once [Apprentice] Doppelganger spawns>
(Luther)
A doppelganger appeared?
I see, that's what [Apprentice]'s
Darkers appearing means.
(Matoi)
...[Apprentice]!
<After the doppelganger is defeated>
(Matoi)
...We have to defeat the remaining Darkers![/spoiler-box]
The second cutscene
[spoiler-box](Luther)
How's it? Isn't it fascinating?
This is [Double]'s inner universe.
A congregation of the things that got eaten, a chaotic space.
If you've fought them, you must have
seen their ability too.
The ability to clone their prey.
Summoning the things that are born in
the inner universe into the real world.
Perhaps it could be called a parallel universe.
Capture it, arrange it, summon it.
...Ahh, examining it is so fascinating.
With this information, I could make
even better clones...!
(Matoi)
Silence!
I'll never forgive you for Xion's death...!
Toying with ARKS, bringing everyone pain,
it's all because of you...!
(Luther)
"Bringing everyone pain"?
If that's the case, why didn't
Xion stop me?
(Matoi)
...Huh?
(Luther)
She's an entity that surpasses people.
Even though I was in control,
she probably had the means to intervene.
And yet, she didn't intervene with
neither the creation of ARKS nor clones.
On the contrary, she produced the
ultimate existance herself.
(Matoi)
...Ultimate existance?
<At this point, the player silently objects to Luther talking about it.>
(Luther)
...Well, it doesn't matter now.
Just, don't forget.
The fact is, before ARKS was created,
this world was already Darker territory.[/spoiler-box]
Field conversation after second cutscene
[spoiler-box](Matoi)
We need to leave this space quickly...
Let's hurry up!
[Player]!
<House toy darker spawns. Luther gives tips on how to defeat it but too lazy to translate.>
(Luther)
It's better to go north.
Whether you follow my instructions or not
is up to you.
((If Luther's directions are ignored again, I don't remember the context so I can't translate it properly. But he comments on the repulsive things [Double] ate.))
<Upon teleporting and getting ambushed by bear and rabbit darkers>
(Matoi)
...!?
(Luther)
An ambush, is what they're doing.
Doesn't that just turn your head?
((Not really sure on how to translate this.))
<After defeating them>
(Luther)
East.
No words are needed beyond that, yes?
<If Luther's directions are ignored>
(Luther)
Won't you listen to my advice for once?
This is a roundabout way.
I recommend the way I instructed.
This is what happens when you don't listen to my advice.
...Ah yes, if you use the turret over there,
couldn't you mount a counterattack?
Oh, they're still coming.
They have quite a spirit.
You really like to take your time, don't you?
Or I wonder if you're doing it to spite me.
Well, all enemies have been defeated.
Let's keep going, even though this is
a roundabout way.
<Once bird darkers spawn>
(Luther)
Fufufu... I see, I see.
Are they going to appear here?
You have a quite good taste, don't you, [Double]?
<Once Loser doppelgangers spawn>
Hm, my clones were made with a discerning eye.
However, isn't the quality really bad?
<Once Falz Angel spawns>
(Matoi)
Even that...
(Luther)
Oh, even when preying under those circumstances,
you can still clone up to this point?
Impressive, [Double].
((I'm not sure what Luther is saying after Falz Angel is defeated.))
((Car darkers spawn, Luther explains, I'm too lazy, etc etc))
(Luther)
It's better to go east.
Feel free to wander around if you want.
<If headed into dead end instead of following directions>
(Luther)
Seriously... Even though this place had some amusement in it,
is it fine to do this at your leisure?
<After the Caterdran is defeated>
(Luther)
Come now, return to the path I guided you.
You can't go wrong with going east from here.
<If going south instead of following directions>
(Luther)
I wonder if you enjoy taking detours like this.
Oh well, I won't stop you.
We have time, since it's close to infinite.
It seems like we can't turn back.
Let's keep going this way.
<Once Elder doppelganger spawns in detour route>
(Luther)
...I see, [Elder] doppelganger.
((Not sure what he says after this. Talking about his Darkers
appearing beforehand, I believe.))
<Once Falz Hunar is defeated>
Is this a display of having eaten [Elder] as well?
At this rate, this is a poor quality doppelganger.
...Did you really eat all of them?
Besides yourself, didn't you eat all of them?
What now, huh, [Double]?
((Interesting to note that the Elder doppelganger talks exactly like Hunar, just in a more Gettemhart-like voice. He also lacks a lightning weakness.))[/spoiler-box]
The third cutscene
[spoiler-box](Luther)
You're making a scary face, young lady.
Is it because you're discontent with the
facts stated earlier?
(Matoi)
Obviously...!
Speaking of the origin, you Photoners were
the source of the Darkers' creation.
(Luther)
But, that which became the origin of all Darkers,
[The Profound Darkness]'s creation, is deemed to be
Xion, young lady.
At that time, she probably would have noticed.
With her calculation abilities, she could have
predicted the future to some degree.
Such as the consequences of [The Profound Darkness]'
creation and what would become of the Photoners.
And know the results.
Because the Photoners were fighting [The Profound Darkness],
they lost their powers of controlling photons,
and ARKS was created.
Even though [The Profound Darkness] was sealed away,
Dark Falz remained.
Thus, ARKS and Darkers have always been fighting.
Even now, they continue to fight.
A pointless fight, you see.
(Matoi)
It's not pointless!
(Luther)
No, it is pointless, young lady.
...Each Dark Falz bears
a respective desire.
And then, that desire is influenced by
that which they're drawn to, being further distorted.
[Elder] should be easy to understand, right?
As a result of being influenced so strongly,
he has forgotten his true purpose, seeking only conflict.
[Apprentice] as well, [Loser]...
Me, well, there wasn't much difference.
But, only [Double] is different.
Only [Double] wields that strength to
realize their true purpose.
(Matoi)
True purpose...?
(Luther)
It has been decided.
[The Profound Darkness]' revival.
A way of one-handedly reviving [The Profound Darkness].
Which is to eat all the Dark Falz.
If the Darkers' origins are all gathered equally,
[The Profound Darkness] will be revived before long.
Think about it.
[Double] has eaten [Apprentice] and [Loser].
Then probably also ate [Elder].
The countdown has already begun.
The countdown until this world's destruction
due to [The Profound Darkness]' revival.
<Here the player is given a choice to say "Then we need to defeat [The Profound Darkness]" or "Defeat [Double] before that happens">
((I only know what he says about defeating Double since I never selected defeating PD.))
<Response to defeating Double>
(Luther)
Indeed, that's the only way to do it.
If [The Profound Darkness] is revived,
it can create as many Dark Falz as it wishes.
Even just [Double] would be a difficult battle.
You have no chance of winning.
Moreover, I'd like to remind you that
you're currently situated
in [Double]'s stomach.
(Matoi)
...I don't understand.
What in the world is [The Profound Darkness]?
Why was such a thing made?
(Luther)
...[The Profound Darkness] is an imitation of Xion.
Produced by the Photoners to be
an artificial Akashic Record.
Bearing the ability to calculate and gifted with
judgment through photons, it acted as a management
agent for everything. An artificial
Akashic Record because of mankind's sloth.
But, mankind back then was nearing the end of its civilization.
At the peak of its sloth, a negative emotion got mixed in
during the course of making it. That's what produced it.
Photons are strongly affected by emotions.
The more of them there is, the more drastic the
change caused by them is due to changes in underlying emotions.
As a result, [The Profound Darkness] became
an incarnation of negativity, giving birth to Darkers.
In order to destroy the universe.
You asked me, didn't you, young lady?
"Why was such a thing made?"
I, too, tried asking that.
If destruction was foreseen midway
through its creation,
why didn't she stop it?
But, now I understand her feelings a little.
Most likely, she would answer
..."because I was lonely."
((I realize this explanation about PD sounds confusing,
but I'm not entirely sure on how to translate it. _(:3」∠)_))[/spoiler-box]
Last cutscene/field quote
[spoiler-box]<Field line>
(Luther)
There's a Darker presence.
Furthermore, it's a considerably powerful one.
...Are you really prepared?
<Cutscene>
(Luther)
...Well then, up to now I was
telling you about the outside world.
I intended to tell you about
[The Profound Darkness]' revival.
Which means guaranteed destruction.
That is, a world where only pain exists.
...Even so, are you willing to go back?
<The player is given the choice to respond with no hesitation or look at Matoi.>
<Response to agreeing without hesitation>
(Luther)
...Fufu, very amusing.
<Response to looking at Matoi>
(Matoi)
...There's no need to hesitate.
[Player].
Our place to be
...isn't here.
<After either dialogue branch>
(Luther)
...If that is so, you should leave.
Here is the end of the universe.
Prepare Clarissa, gather strength.
Defeat Darkers, devour Darkers.
It looks just like that time.
(Matoi)
Because of that, can I create a path?
((Unsure of how exactly to translate this line.))
(Luther)
It's impossible for me, but
if it's you, it's possible.
Because you are ARKS.
Go forth, masterpieces.*
Show me how fun an uncertain world
which has lost omniscience can be.
((* Although Luther verbally says 「最高傑作」, which means "masterpiece" and is present in
the quest's JP name, the text says 『出来損ない』 instead, which is also in the quest's name,
which translates to "failure" or "badly made".))[/spoiler-box][/spoiler-box]