To save time, Jin used the transporter gun Reiko possessed to return to Hourai Island via Shinkai.
The Jin Family had gathered there to welcome him back.
"Jin-nii, welcome back. I listened to the report, but I could only understand about half of it."
Elsa, it seemed, hadn't been able to fully grasp the gravity of everything No. 700672 had said.
"Jin! I am far from understanding it myself, but I could tell that a wonderfully profound theory was being discussed!"
"Jin-kun, this is a subject I would love to take my time and tackle."
Saki and Toa sensed that a door to a new world had been opened; even if they didn't fully comprehend it yet, they were visibly excited.
"Jin, I couldn't grasp it all. But you are different, aren't you? I believe that one day you will explain it to us in a way that is easy to understand."
"Jin-kun, I shall be waiting for that day as well."
Reinhard and Stearena honestly admitted their lack of understanding while expressing their hope for Jin to teach them once the commotion had subsided.
"Jin-sama, please do your best. I will cooperate to the best of my ability in whatever way I can."
"As will I."
Mine and Berche sincerely offered their support.
Surrounded by his reliable family, Jin truly felt how blessed he was.
They continued their discussions late into the night.
Starting early the next morning, Jin immediately took action.
First was the development of the magi reactor.
It was a technology that Negadoll 001 likely possessed as well, and in order to prevent an ether stampede, he needed a more efficient power source.
"Hmm, so I need to combine the ether converter and the mana driver into one..."
Jin fell into deep thought. Packing both functions into a single magi-crystal was simply impossible.
Inevitably, they would have to be arranged on a link board to function, but losses would always occur during connection and synchronization.
The devices created by Jin, the previous Magi Craft Meister, and Adriana boasted incredible efficiency, but even then, losses existed.
Once, when Reiko had been captured by a Gigas, she had destroyed the giant's core by providing an excessive supply of mana. At that time, the loss of mana had caused the surroundings to glow with a blinding light.
Looking back at that, it was clear that even Jin hadn't managed to reduce losses to absolute zero.
"Hmm, Fusion isn't enough..."
As Jin sat there racking his brain, Stearena poked her head in.
"Jin-kun, do you have a moment?"
Since he was currently stuck, Jin welcomed the interruption.
"Did something happen?"
"No, I just happened upon something interesting and wanted you to see it."
As she spoke, Stearena held out her right hand and opened her palm.
"This is..."
"Interesting, isn't it? I found it by chance while I was looking for various crystals."
It was a crystal consisting of two flat quartz crystals joined together.
It was what was known as a "twin," where two crystals grew together at the same time. Unlike two crystals simply being stuck together, it had a geometric regularity.
Memories of seeing a specimen in his middle school science lab resurfaced.
In quartz, these were called "Japan Law twins," and their flat shape resembled a butterfly spreading its wings, which had left a strong impression on him.
"...Jin-kun?"
Just as Stearena began to look at him suspiciously for falling silent while staring at the crystal, Jin "rebooted."
"I see! That's it!...Stearena, thank you!"
"I... don't really understand, but I'm glad I could be of help. So, about this crystal..."
"Ah, this is called a 'twin,' and it's not just crystals being stuck together..."
Jin explained as much as he knew about twins.
After thanking him, Stearena returned to her own workshop.
Jin, on his part, immediately began to weave his magic to give shape to his idea.
"What if I combine Fusion and Crystallization?"
He tried it out with the quartz he had prepared. The two crystals melted together and crystallized again.
"Hmm, that's not quite right."
It simply resulted in two crystals being stuck together.
"Do I need to combine one more thing... Fusion, Crystallization, Forming... No, that's not it either."
He only ended up with a misshapen crystal.
"Fusion, Crystallization... Stransform!"
By using Analyze to grasp the crystal structure while simultaneously changing that structure, Jin developed a technique that could be called a masterstroke of magi craft.
And there before him sat a magnificent Japan Law twin.
"I did it! With this, I finally have a path forward for the magi reactor."
Magi-crystals were normally processed into spheres. That shape was chosen empirically because it was easy to shape, aesthetically pleasing, easy to handle, and because a sphere has the smallest surface area relative to its volume.
It was believed that the smaller the surface area, the more effectively the contained mana could be used. The reason why remained unknown.
Jin was now daring to defy this empirical rule.
Original magi-crystals had a structure very similar to quartz—in other words, a hexagonal prism. The magi-crystals generally in circulation were pieces carved out from those.
However, Jin wondered if he could take advantage of the crystal's natural shape. Specifically, he intended to utilize the flat surfaces.
"If I write the magi-formula directly onto here, I won't even need a link board, and it'll be easier to control!"
Jin realized that by treating the crystal's shape itself as the link board, he could achieve a level of precision control that was impossible with a sphere.
It was a technique that would have been useless if he couldn't manufacture Japan Law twins, but for Jin as he was now, it held immense promise.
After another hour of trial and error...
"It's done!"
He had finally completed a magi reactor with an efficiency of over 99 percent.
With the previous combination of an ether converter and a mana driver, he had never measured it accurately, but it likely topped out at around 80 percent.
Even that was an astounding figure, but the magi reactor he had just finished was over 99 percent. It was an outrageous level of efficiency.
"I'll install this in Reiko and everyone else, and then..."
Jin immediately began thinking of applications.
"In any case, I'll have to mass-produce them."
Next, Jin decided to tackle his next challenge.
Naturally, it was a countermeasure against Negadoll 001.
"First, I'll start with countermeasures for the ether stampede."
The total domination of free ether. That was exactly why he had developed the high-output magi reactor.
"A magic that turns mana back into free ether, huh..."
Jin suddenly thought of something. The Gigas—flawed though they were, they were the ultimate weapons for the final battle against the demon race. They also possessed a function to absorb the surrounding mana. Since they had all been destroyed, he had never figured out the method they used.
"Those might have been things that Negadoll 001 provided to humanity as well..."
Given their nature of attacking both friend and foe once activated, it seemed plausible.
"...Anyway, for now, I have to focus on this development."
Jin decided to generate a magi-crystal to produce the mana waves that would control free ether.
The base was a light-attribute magi-crystal. It was a crystal very similar to transparent quartz.
"I'll add the mental catalyst I received to this."
When he opened the box, it contained a pinch of black powder.
Following the instructions he had been given, Jin added it at a ratio of 1 part to 100 parts magi-crystal by weight.
"Add."
The transparent magi-crystal turned a murky shade, resembling smoky quartz.
"If I use this in a generator, I should be able to exert a great influence on free ether."
He should be able to cast the Magic Cancel spell he had been thinking about before.
He named the device the Magic Canceller.
By forcibly returning mana into free ether, he could erase an opponent's magic, with only a few exceptions.
The exceptions were pure physical attacks, like throwing a stone to hit someone; once the magic was triggered, it no longer required a supply of mana, so the canceller would have no effect.
Other than that, for example, fire-type magic would be extinguished, and wind-type magic would dissipate. He should even be able to cancel Gravity Magic and interfere with Teleportation Magic.
Considering the limited amount of powder he had, he restricted himself to making only two.
One would be for Reiko's use, and the other would be for support from the air.
"The rest will go toward Reiko's ether stampede countermeasures."
As his trump card, Reiko was highly likely to be incapacitated by an ether stampede in her current state. Furthermore, considering the possibility that Negadoll 001 could use ultra-powerful Master-Slave Magic, Jin was planning to apply an even stronger shield to her.
When he contacted her via manacam, Reiko arrived immediately.
"Father, did you call for me?"
"Yes, Reiko. I've called you back to reinforce you even further."
Jin explained the details and purpose of the modifications to Reiko. Without a moment's hesitation, Reiko nodded.
"Yes, please do."
And so, Jin threw himself into the task of modifying Reiko with everything he had.