Jin explained the three-dimensional magic circle in detail to the assembled Jin Family.
"...In other words, we can create magi-devices without needing magi-stones or magi-crystals. Though its applications are strictly limited, of course."
Reinhard was the first to chime in.
"So while it suffers from low output and struggles with sudden output fluctuations, its main advantage is that it allows us to manufacture magi-devices cheaply."
"That's exactly it."
"Even if its uses are limited, it sounds like it could be applied to plenty of everyday consumer goods. Things like streetlights or heating," Beena noted. Her former reputation as the Craft Queen certainly wasn't just for show.
"Right. It should be plenty useful for light magi-devices, including nightlights."
Mana consumption was low, and once switched on, it could simply be left running until daylight returned.
Heating was much the same. The only real difference from lighting was that the temperature regulation cycle—turning off when it got too hot and turning on when it got cold—ran on a slightly shorter rhythm.
"Could it be used for water pumps?" Louis asked. "If all that's required is a steady pumping volume, that doesn't sound too difficult."
Reinhard addressed the question.
"Yeah, exactly as you say, Louis. The catch is that the output is relatively small, so unless we configure several units to run in parallel, you'd probably only get a trickle."
"I see. But as long as that works, practical application shouldn't be much of a hurdle, right?"
"No, not at all. At a glance, wiring five sets in parallel should deliver performance on par with, or even exceeding, a standard magi-device."
Jin agreed with Reinhard's estimate.
"I'd say so. Compared to using magi-crystals, the cost of a magic circle setup... well, even running five in parallel would bring the cost down to somewhere between half and a quarter."
"I thought it might become even cheaper than that, but I suppose not?"
Seeing Louis's slight disappointment, Beena explained.
"Dear, that's only natural. For simple lighting it might be cheaper, but with a pump, mechanical components make up more than half the total cost."
"Ah, that makes sense. Fair enough."
Convinced by her explanation, Louis nodded.
"So ultimately, is the problem what you'd call the operational efficiency of free ether? Is it just too low?" Hanna asked.
"Pretty much," Jin answered.
"Then where does the issue lie? The magic circle itself? Or the medium?"
"Uh... well..."
Hanna's pointed question left Jin momentarily at a loss.
"I get that regular paper keeps costs down. But what happens if we use slightly higher-grade materials—like, say, magical beast hide?"
Which would have the greater impact: the boost in efficiency, or the surge in cost? That was Hanna's angle.
"We don't really have a good way to compare prices here on Hourai Island... Laojun, can you tell us?" Jin asked.
"Yes, My Lord, everyone. Depending on the species of magical beast, general market rates put the unit price per square meter anywhere between roughly one thousand and ten thousand Toll."
Approximately ten thousand to one hundred thousand yen.
Naturally, dragon-type materials were excluded from the estimate since they were never traded in general markets.
"Over a hundred times more expensive than paper, then... The cost far outweighs the benefit."
The most economical way to assemble a three-dimensional magic circle was through layering.
In terms of sheer thickness, paper was an ideal candidate, but its mana conductivity was regrettably poor.
On the other hand, turning to magical beast hide would drive costs through the roof without offering a proportionate leap in performance.
"Kufu, and that's precisely where magi-type processing comes into play."
Saki spoke up.
Back when Jin was staying in Avalon, she had caught wind of the technology through Laojun and had been quietly conducting her own material research ever since.
"Instead of ordinary paper, I ran tests using paper made from Hourai Island timber that had been aged in a free ether box for a week. The efficiency improved by about one percent."
"And what caused that?"
"Better conductivity toward mana."
One percent over a single week. Whether a full year of aging would yield a fifty percent increase remained entirely unproven, Saki concluded.
"That being said, the real catch here is that you can't expect those results unless you use paper sourced directly from Hourai Island."
Which meant ordinary commercial paper wouldn't cut it. Jin's shoulders slumped in disappointment.
"I did try another avenue, though, Jin," Saki added, offering an encouraging smile.
"Which was?"
"Impregnating regular paper with a coating that has favorable mana properties."
"I see. Something like magi-resin?"
"Spot-on, Jin! Exactly that!"
According to Saki's experiments, treating commercially available paper with magi-resin boosted its mana conductivity by fifty to seventy percent.
"Hmm, but wouldn't that still be a net loss cost-wise?" Reinhard pointed out. "Not to mention, magi-resin can only be manufactured here."
Saki responded to Reinhard's objection with a wry chuckle.
"You're quite right, Reinhard."
"Hmm... Is there really no practical way forward, then?"
Just as Jin was about to lose heart, Saki cut back in.
"Come now, Jin, hear me out to the end!"
"There's another magi-type material readily available on the open market, isn't there?"
"Wait, what?...................Oh! Magi-resin!"
"Bingo! As expected of our Jin."
Saki showered Jin with unreserved praise.
"Magi-resin can't be rolled thin on its own, but it's a completely different story once you impregnate paper with it."
"That's true."
Modern Japan had similar composite substrates for electronic circuitry, such as paper phenolic boards.
"And with this method, mana conductivity improves by forty to sixty percent. The cost doubles, though."
"That's a bit borderline."
"Even so, considering how cheap the base material is to begin with, the final unit cost remains well within practical limits."
For applications where compact sizing was essential, the performance vastly outperformed plain paper while keeping expenses comfortably low.
"Fair point."
Jin readily conceded.
"Kufu, if we take paper crafted from Hourai Island wood, impregnate it with Hourai-produced magi-resin, and then age it in a free ether box, we could easily see efficiency triple."
"Even then, we're still falling a bit short."
Jin wanted one more decisive breakthrough.
"Leave that part to me—I'll push the research further."
Saki gave a confident nod, reassuring him that she would handle it.
Just then, Goose spoke up.
"Jin, Saki, a thought just crossed my mind. What about mica?"
"Mica, huh..."
Mica, also known as muscovite, possessed a crystalline structure that naturally cleaved into razor-thin sheets.
Thanks to its fracture resistance, Jin had once used muscovite sheets as a glass substitute for windows back in Kaina Village.
"Yes, yes, that's brilliant, Goose!"
Thrilled at having found her next research subject, Saki lit up with excitement.
"Jin, I'm going to look into this right away!"
"Yeah. I'm counting on you."
Reassured by Saki's infectious confidence, Jin gladly entrusted the task to her.