"Something you want to show me? You... to me? What would that be?"
At Jin's question, No. 700672 allowed a smile to touch his lips.
"Pray, do not be in such a hurry. Won't you first introduce the young lady you've brought along?"
Jin sheepishly scratched his head.
"...This is Elsa. She’s my fiancée."
No. 700672’s gaze traveled slowly from the crown of Elsa’s head down to the tips of her toes. It wasn't an intrusive or unpleasant look, but rather one of clinical and appreciative observation.
"I see. So this is Elsa-dono? The one you previously described as a gifted disciple, an excellent healer, and a precious member of your family?"
"J-Jin-nii!?"
Elsa's eyes went wide, and she turned a shade of pink at hearing such high praise from No. 700672's mouth.
"Hehe, so it would seem....Hm. Your Mana Overload Syndrome has been cured. The mana circulation within your body is in perfect order."
"Yes. One reason I came today was to thank you for that," Jin said.
"Thank you very much."
Both Jin and Elsa bowed deeply to the homunculus.
"There is no need for thanks. I, too, have been much indebted to Jin-dono. Being able to walk about like this is thanks to him."
Beside him, Neige beamed with happiness.
"Oh, I should also introduce Edgar. He’s the first Automata Elsa ever built."
"Oho? To produce an Automata of this caliber on a first attempt... truly impressive."
"T-That’s only because Jin-nii was such a good teacher," Elsa said, looking down bashfully.
No. 700672’s smile remained warm. "No, that is not all. To achieve such a high quality of Finish without neglecting even the smallest detail is a testament to your own innate talent."
Off to the side, Reiko and Neige were deep in conversation. Or more accurately, Neige was chattering away with unrestrained excitement.
"Father has been so much better lately!"
"He can walk now! And he pats my head all the time!"
"He even made these clothes for me the other day!"
Reiko nodded along politely, offering small smiles. "I see. That’s wonderful."
"It is! And also..."
Leaving the two of them to their catching up, Jin turned his attention back to No. 700672 to state the primary reason for his visit.
"I’m certainly interested in what you have to show me, but I actually came today because I wanted to ask about free ether."
"Oho? Free ether, you say? What is it you wish to know?"
Jin proceeded to explain his concerns regarding energy depletion, referencing the resource crises he knew from his previous world.
"I see, I see. So your world faced such a dilemma. And you fear the same fate might befall the free ether here?"
"Exactly. Usually, I'd take my time to research and figure these things out on my own, but I felt this was a matter that shouldn't be left to chance."
"A wise sentiment. Very well, I shall explain."
No. 700672 gestured for Jin to follow him to a table at the back. Elsa followed close behind. Jin told Reiko and Neige they were welcome to keep talking where they were.
The tabletop functioned as a magi-screen. As No. 700672 moved his fingers across the surface, diagrams began to form. He drew two circles: one large and one small.
"To begin with, our conclusion is that free ether is likely a particle that exists in the state between matter and energy."
While Jin lacked a deep background in quantum mechanics, the explanation made intuitive sense to him.
"It is small enough to permeate the atomic structure of ordinary matter and light enough to be manipulated by mental waves. Furthermore, it is easily converted into various forms of energy. These observations led us to that conclusion."
"I think I understand," Jin said with a nod.
"Good. We never achieved definitive proof, mind you. It was simply the result of empirical observation and the systematic elimination of other hypotheses....But that is merely the introduction."
No. 700672 pointed to the diagrams on the magi-screen.
"First: where is free ether born? It is here."
He tapped the large circle.
"...The sun?"
"Precisely. Free ether is generated by the reactions within the sun’s core, released alongside light, heat, and various electromagnetic waves."
Jin felt a heavy weight lift from his chest. "Which means..."
"Yes. There is no need to worry about depletion."
If the sun were to ever stop producing ether, the loss of energy would be the least of their problems—it would signal the end of the entire solar system.
"So we should be safe for several hundred million years, then."
"Indeed. My masters utilized free ether as if it were an infinite well, yet never once did they see even a hint of it being exhausted."
Jin let out a long, silent breath of relief.
"Now, for the next point."
No. 700672 pointed to the smaller circle.
"If the large circle is the sun, let this smaller one be our planet, Ars. The free ether produced by the sun radiates out into the void of space. A portion of that radiation reaches Ars."
Jin nodded, listening intently.
"We believe that the planet’s internal structure, the elements it contains, and its rotation create a specific effect: the North Pole attracts free ether, while the South Pole repels it."
"I see... that explains a lot."
"We speculate that the free ether drawn in at the North Pole is subjected to immense pressure within the planet, where it eventually crystallizes into magi-crystals."
No. 700672 looked slightly disappointed as he added, "Unfortunately, we were never able to confirm that part of the theory."
"Still..."
Even if it was just a hypothesis, it provided a logical framework. It also finally explained why ether concentrations were so low toward the southern regions of the world.
"Of course, this hypothesis could be flawed," the homunculus admitted.
But for Jin, the most critical part was the source of the energy.
"So, in short, free ether is produced by the sun, drawn in by the planet, and fills the environment around us?"
"Exactly. There is no doubt that it is born from the sun."
That confirmation washed away Jin’s lingering anxieties.
"Jin-nii, that's such good news," Elsa said, her expression softening with relief.
"It was worth coming today just to hear that." Jin bowed his head in gratitude.
"I am glad I could put your mind at ease."
No. 700672 then turned to the second reason for their meeting.
"When you dealt with the Failure previously, we spoke briefly of transporters, did we not? I recall your reaction suggesting you did not possess such a device."
A transporter was a device that could send objects to, or retrieve them from, a specific location marked by a marker. While Jin’s own transporters could send objects to any coordinates, they lacked the ability to bring them back.
"As such, I have assembled a latest-model unit for you. I would be honored if you would analyze it and apply its principles to your own work."
The phrasing—analyze and apply—showed just how well No. 700672 understood Jin’s nature as a craftsman.
"Thank you. I’ll make good use of it," Jin said, accepting the gift with both hands. In return, he produced the gift he had prepared. "It’s a bit late, but I brought this for you."
When he saw the Persica juice, No. 700672’s face lit up.
"Oh, this is a welcome sight. While I do not strictly require sustenance, this is a great help. Drinking it keeps me in peak condition for several days."
Since it was a plant-based organic compound, it was one of the few things even an advanced being like him couldn't easily synthesize. He immediately opened a bottle and drank it down.
"...Ah. It is as potent as ever. You have my thanks."
Setting the bottle aside, the homunculus continued.
"The ultimate goal, of course, would be a transporter capable of warping oneself to any arbitrary location. However, even we were never able to develop such a thing."
"Is that so? I’ve been trying to figure out how to do that myself."
To transport oneself—a true warp engine. If such a thing existed, space exploration and travel between worlds would be a reality.
"Yes. During the several years it took to travel from Hale to Ars, my masters worked tirelessly to develop such an engine... but they ultimately failed."
No. 700672’s expression turned somber.
"...Though, by that time, my masters were but shadows of their former selves. Perhaps it was a feat beyond their diminished strength."
Hearing that even the ancient masters couldn't achieve self-warping—at least not through the extension of transporter tech—left Jin feeling a bit deflated. It seemed the path to a true warp engine would be even more difficult than he had imagined.