While Jaden and Yubel dueled, Hikaru was deeply absorbed in research.
On one hand, he needed solutions for every current problem. On the other, the massive number of cards obtained from Darkness's faction were all usable materials.
At this point, Hikaru had essentially no weaknesses in card research. The only thing limiting him was "Pendulum" cards.
Pendulum cards were genuinely something Hikaru couldn't manufacture.
Despite having extensive data taken from Z-ARC, different fields required different expertise. Hikaru's alchemy was decent, but his scientific capabilities weren't at that level.
Zone had only provided Darkness data, since that was more urgent. Zone hadn't had time to analyze Pendulum cards either, leaving Hikaru completely in the dark on that front.
Of course, even without making Pendulum cards, the massive number of cards obtained from Darkness gave him plenty to work with for crafting various cards.
For example: Super Polymerization.
After dueling the Supreme King, Hikaru had been considering how to create Super Polymerization from scratch using his knowledge and skills.
Although the Darkness-sourced cards contained vast dark power for experimentation, replicating or "extracting" more of Super Polymerization's true power wasn't that simple.
Fortunately, through trial and error, he had identified several possibilities.
First: recreating Super Polymerization through "Fusion Monsters."
Just as combining Infernoid and Qli components had revived and awakened Tierra, that process itself was a form of "intention" and "symbolism."
Similarly, recreating Super Polymerization through Fusion Monsters used a comparable method.
This approach came from studying Professor Seraph's "Demon Summoning Studies" and researching his "Revelation Records."
By creating twelve different Fusion Monsters spanning Levels 1 through 12, then using a specific method for "reverse" Super Polymerization, a second, controllable Super Polymerization could be born.
Yes, a controllable Super Polymerization!
Actually, a slight complication had recently emerged.
Hikaru discovered that his gradually improving mastery of Super Polymerization, his ability to use auxiliary cards during duels, was becoming harder to control again.
This wasn't obvious. Clearly, he hadn't "gotten weaker." On the contrary, his spirit power had increased a level, nearly reaching human limits.
If he was stronger yet the previously easier-to-handle Super Polymerization was harder to control, the implication was simple.
His Super Polymerization had begun growing stronger after he defeated the Supreme King.
Or rather.
The "assistance" he received from the concept of "Fusion" was growing stronger.
Tierra theorized this might be like the Synchro Dimension's gods competing for the "Synchro" concept. Hikaru and the others with Super Polymerization were "Super Polymerization's emissaries." Unlike the Synchro holders who had their own consciousness, Super Polymerization itself had none.
Or perhaps Hikaru and the Supreme King were this world's equivalent of "Earthbound Gods."
She couldn't help laughing at her own theory, finding it absurd.
But thinking deeper...
It actually made sense.
In any case, Hikaru's share of power from the concept of "Fusion" had increased. Super Polymerization had grown stronger, providing him with more cards. Even some cards that theoretically required specific powerful spirits to create, like Fusion Monsters that only "The Eye of Timaeus" or "The Claw of Hermos" themselves could birth, Hikaru could now attempt to craft.
Naturally, Hikaru's primary research subject during his spare time had been "Time Magic Hammer."
Time Magic Hammer was a Level 2 LIGHT Spellcaster Fusion Monster. As a Fusion Monster, it could only be Special Summoned by using The Claw of Hermos's effect to send a Spellcaster from hand or field to the Graveyard.
Unlike The Eye of Timaeus, which could directly transform Dark Magician or Dark Magician Girl into Fusion Monsters, The Claw of Hermos primarily turned monsters into "equipment" to support other cards in battle.
Honestly, Time Magic Hammer's effect itself wasn't particularly critical for Hikaru.
But one thing was important for Hikaru and his future goals...
It was a Level 2 Fusion Monster.
That might not sound like a big deal.
But across the entire Yu-Gi-Oh! card pool, Level 2 Fusion Monsters numbered only three: Time Magic Hammer, Mudragon of the Swamp, and the universally despised Runick Winged Hugin.
Hugin needed no discussion. Hikaru had never even seen a Runick card. Super Polymerization hadn't even given him one, despite Runick being entirely Fusion-based.
As for Mudragon of the Swamp, it was a Fusion Tuner Monster requiring two Normal Monsters as materials.
Hikaru hadn't found it in the Forgotten Realm, so he could essentially assume it was out of reach for now. That meant the only obtainable "Level 2 Fusion Monster" was Time Magic Hammer.
Conveniently, he still had The Claw of Hermos.
Of course.
After conceiving the possibility of using twelve different Fusion Monsters from Level 1 through 12 for Super Polymerization replication, Hikaru had naturally also considered using "different types of Fusion" for reverse Fusion to copy Super Polymerization.
But compared to the referenceable "Super Fusion God" concept from the original story, recreating Super Polymerization through Fusion was far more complex.
Hikaru had absolutely no leads.
Was it all "Deck Fusion" cards? "Graveyard Fusion"? "Recovery Fusion"? "Fusing the opponent's monsters"? Or "Fusion that can't be responded to"? Or maybe one of each?
Too many possibilities. Hikaru would need dedicated time for repeated experiments to narrow down the options.
Additionally, there was another replication possibility: "using monsters that can perform Fusion on their own." Specifically, monsters like Ancient Gear Hunting Hound, Predaplant Sundew Kingii, Edge Imp Sabres, Frightfur Sheep, and Crowley, the Gifted Magistus, which could Fuse simply by being on the field.
Regardless, if Hikaru could successfully create a "second" Super Polymerization, he could keep the "power-rich" original safely worn on his person while placing the ordinary Super Polymerization in his Deck. This should reduce the risk of Deck cards being consumed by Fusion and greatly improve his dueling stability.
Beyond these spare-time analyses, Hikaru's main research direction had been steadily advancing.
Namely, "Infernoid Nehemoth" and "Hidden Qli Machine Killer - Materialism."
Without sufficiently powerful card bases, and with nobody gifting him another Psychic End Punisher, Hikaru had been unable to complete experiments on these two cards.
The latter wasn't urgent. Hikaru figured there was no rush.
Since he couldn't make Pendulum cards anyway, no matter how much Tierra pressed, he couldn't conjure one.
Besides, Tierra at this point was far less desperate than she had been initially.
Or rather, Tierra had never really cared much about time.
The Infernoid was nearly complete. Working with Hikaru was so enjoyable and smooth. What was there to rush?
Of course, despite Tierra not being anxious, Hikaru still thought it best to finish Nehemoth sooner.
On one hand, although he already had "Infernoid Tierra," it was crafted by the Light of Destruction and was incomplete, still flawed in power.
On the other hand, Hikaru couldn't keep using The Dark Hex-Sealed Fusion as a Nehemoth substitute forever.
Not that it didn't work, but substitute materials were ultimately substitutes. In critical moments, they couldn't perform their full function.
For example, Hikaru's "strongest" opening play, the Equip version of Future Fusion, desperately needed Nehemoth.
The reason was simple: The Hex-Sealed Fusion couldn't act as a substitute material while in the Deck!
Although substitutes were more versatile in most situations, they couldn't replace the original in the Deck. So he couldn't execute his strongest play: Future Fusion dumping eleven Infernoids, Fusing Tierra, milling Evil HERO cards to search Helshaddoll Hollow, then immediately deploying three powerhouses.
The Infernoid monsters shouldn't be underestimated.
Hikaru had never used their effects in previous duels, but that didn't mean they lacked effects or that their effects were useless.
Every single one had formidable effects!
Especially Nehemoth and Lilith, which came with built-in "Spell/Trap negate" and "Monster effect negate" respectively. One card stripping the opponent's hand plus two negates plus unknown Set cards? Forget this world; even in his pre-transmigration world, that was enough to win.
Hikaru held up a card and examined it carefully.
Infernoid Nehemoth. Level 10, FIRE Attribute, Fiend-Type. ATK 3000, DEF 3000.
On the card, a red dragon demon bearing a colorful divine ring, wings spread wide, emitted bursts of laser light. But soon, the light faded, and the blue hellfire slowly subsided.
Still not enough.
Although he had used several of Mr. T's cards in the crafting, it still wasn't enough. But at least the basic prototype had stabilized. From here, he just needed to do what he always did: craft it gradually.
No big deal.
In contrast...
Hikaru picked up another card.
Unlike the flickering Infernoid Nehemoth, this "Hidden Qli Machine Killer - Materialism" simply refused to be born.
Despite preparing materials that were among the world's rarest "Pendulum Monsters," even cards created by that "G.O.D."
All this effort with no success meant only one thing: this card genuinely couldn't be born.
Most likely, until "Pendulum" was fully realized, Materialism simply couldn't come into existence.
He put the card away.
Then he began examining other matters.
Zone's data. Atticus's memories. The comatose students' sensations and mental states. The momentary "ripple" from Echo's ship collision. The fragments Tierra had collected when she first burned the wall with purgatorial fire...
All this information, gathered over time from friends and allies or collected personally, was being studied by Hikaru and his spirits. Their goal was singular: lock onto one set of coordinates.
The coordinates of the Reverse World!
All this time, facing every action by Darkness, humanity could only passively endure, passively seek solutions, passively survive.
They couldn't fight back against Darkness. They could only deal with the enemies Darkness sent.
But Hikaru would never silently endure. Although Darkness's true form had appeared in this world, giving humanity a chance to defeat this previously untouchable "grim reaper," that didn't mean they could simply walk up and fight it.
If Darkness wanted, if it wasn't in a hurry, it could always retreat temporarily. It had plenty of resources, and the invading spirits weren't its own power. Essentially zero losses.
Next time it launched a surprise attack, would they just take it again?
Absolutely not!
Since when was it acceptable to just get beaten without fighting back?! Hikaru personally couldn't tolerate that kind of humiliation!
So his intention had been set from the very beginning.
Find the enemy. Lock onto them. Storm their home. Defeat them! Eliminate them!
Just as he had persistently searched for the Fusion Army's base, he would find Darkness and defeat it!
Otherwise, if Darkness simply walked away, future generations would suffer!
Fortunately, just as Hikaru expected, much like Professor Banner's artificial dimension created with the Philosopher's Stone and Grand Cosmos cards, and the Forgotten Realm that connected to every location, the Reverse World was, by this era's human "science," indeed a type of "alternate dimension."
Naturally, just as Hikaru and Tierra had gradually collected information to locate the "DT World Dimension's" coordinates, the same method applied here.
Hikaru had finally successfully locked onto a dimension. One directly connected to this world.
After confirming this, Hikaru also understood why Darkness could even isolate humanity's dimensional gate systems from thin air.
After all, in the human world, there existed a "reverse dimension" directly linked to Darkness's world!
All it needed to do was "overlay" it. Nothing could be simpler.
If he were to give this dimension a more precise, more fitting name...
This dimension should be called...
The Post-Apocalyptic World.