Just as Jin had predicted, Duke Blue’s request for cooperation from the Third Generation Magi Craft Meister reached Avalon’s World Security Guard on April 27th.
"Ah... I guess I never really did give them a clear way to contact me."
His only real points of contact were Avalon or his mansion in the Empire's capital, Loizart.
"Well, it’s not like people often have urgent business with me anyway."
The request was for an inspection of the location where the bandit group had discovered their golems. Since it was a formal request from the Kingdom of Egerea to the Celuroa Kingdom, it had taken about two days for official permission to be granted.
If the World Security Guard had acted alone, it would likely have been much swifter. The same applied to Jin, in his capacity as a Magi Craft Meister.
"Laojun, since the opportunity has arisen, please handle it using Jin D."
"Understood."
Since he had already scouted the location himself, Jin decided to let his Body Double handle the official response.
More than that, he wanted to focus on completing his own version of the system as a mark of respect for the nameless magi engineer who had originally developed the magic-frame style.
In his stead, Jin asked Reiko to accompany Jin D.
"Reiko, I might have overlooked something when we were there. It would be a huge help if you went back to take another look."
With Jin putting it that way, Reiko couldn't find a reason to refuse, though she departed with a hint of reluctance.
＊ ＊ ＊
Meanwhile, Jin had begun the work he truly wanted to do at the laboratory on Hourai Island.
"Jin-shama, this is such a fascinating structure."
While Marikka had declined to accompany him to the Fort Phutokes Ruins, she had enthusiastically joined the task of analyzing the magic-frame style golems and establishing a formalized system for them.
"Jin-sama, wouldn't the selection of materials be the most critical part?" Rubina asked. As the First Generation Magi Craft Queen, she already had a sharp eye for the basics.
"Jin-sama, looking at the magi-circuits here, it seems like they could be improved further," added Greena, the descendant of House Kuzuma.
"You're both right. Materials, shapes, controls—they're all still in the early stages of development. That’s exactly why this project is so rewarding, don't you think?"
"Exactly! Jin-sama, thank you for inviting me!"
"It’s wonderful. I'm having a lot of fun."
Both Rubina and Greena seemed to be thoroughly enjoying the work. Marikka was clearly just as invested.
"Using the prototype I built as a base, I want us to aim for a more perfected version."
"Hmm... I suppose the biggest key is the synchronization between the skeleton and the muscles—the drive system?" Rubina suggested.
"Yes, I agree," Greena said.
"True, that is vital," Marikka added, before offering her own perspective. "And then, of course, there's the control system. If that isn't up to par, the rest won't matter."
"Yeah, that’s for sure. Also, when considering it as a mass-production system as a whole, the key point might be the terminal—the magi-machine that creates the control cores."
Jin continued to voice the key points from the perspective of an integrated production system.
"At any rate, we need to solve these issues one by one. Let's start with the materials."
Since he had such talented engineers gathered, they could have easily pursued separate themes, but Jin deliberately chose to have everyone tackle a single topic together.
"First, the skeleton. My first prototype used light silver, but if we want more strength, we should move to 64 light silver."
Light silver was a material with excellent mana conductivity. Consequently, it responded very effectively to Reinforce magic.
"That's true... but I wonder if there's an even better material out there."
"Rubina, we have to keep the cost in mind, too."
"Oh, right."
Ten-year-old Rubina and nineteen-year-old Greena shared a significant age gap, but as fellow descendants of the Kuzuma line, they got along quite well.
"That's exactly it. The reason I called for you all is that I—and the people I usually work with—tend to chase performance while ignoring material costs. I thought this would be a good learning experience for you. In that regard, Marikka designs things with a much better sense of balance, so she'll be an excellent advisor."
"Th-th-that's not true at all! I'm not that... that good!"
Faced with sudden praise, Marikka grew flustered and started tripping over her words.
"I think light silver is a good choice. The unit price is low, and it's plenty strong. What we should really consider is the alloy. We should look into compositions other than 64 light silver."
On the planet Ars, light silver held a position similar to titanium on Earth.
"Next, we look at composite materials and the internal structure."
A primary characteristic of titanium—and thus light silver—is that it is light and strong but relatively susceptible to wear. To counter this, measures like applying an adamantite coating to sliding parts like joints were standard.
While it differed slightly from the technical definition of composite materials, Jin's idea was to use combinations that complemented each other's weaknesses to bring out their respective strengths. As a side note, while many titanium-based alloys are difficult to machine, that was a property irrelevant to those using magi-craft.
"Internal structure... Ah, you mean like making it hollow or using a foam structure?"
Making the inside of bones hollow, using foam, or employing truss structures were all designs inspired by biological life.
"Considering mass production, hollow is probably the way to go."
Anything else would be too time-consuming and therefore disadvantageous in terms of cost. Incidentally, 64 light silver possessed excellent properties, with over 1.7 times the tensile strength of pure titanium. Even for Jin, creating an alloy that exceeded these specs was a daunting task.
He attempted to forge several experimental alloys, but all proved inferior to 64 light silver. Jin decided to conclude his exploration of light silver alloys for now.
"Alright, the material will be 64 light silver. Any parts with a diameter of 20 millimeters or more will be hollow."
With that, the skeleton material was decided.
"The next problem is the material for the muscles. Jin-sama's prototype used Ground Spider resin, but that’s far too expensive for a general model."
Ground Spider resin (GSP) was produced and distributed outside of Hourai Island, but the quantity was limited and the price was steep. To say nothing of the high-grade GSP produced on Hourai Island that Jin had used for his prototype; that was out of the question for a mass-produced unit.
"Jin-sama, what did the bandit's golems use for their muscles?"
"They used magi-resin."
Rubina was genuinely shocked.
"What?! In that case, even if their performance was good, it couldn't have been that impressive..."
"It’s true that standard magi-resin usually lacks both power and speed."
"Right?"
Just as Rubina was about to ask how they managed it, Jin explained.
"However, the magi-resin they used was far higher performance than the standard variety."
Jin offered his theory that the quality likely depended on where it was produced.
"Besides, there's a real reason for using magi-resin."
"...Is there?"
Rubina, who had been born on Onogoro Island and raised in an environment where peak technology was the norm, found this a little hard to grasp.
Jin had experienced this same feeling once before. Four hundred years ago, when he was first summoned to this world from Japan and had just inherited the knowledge of his predecessor, he had felt the staggering gap between that technology and what he saw in Kaina Village, Blue Land, and Port Rock Town. That was precisely why he wanted Rubina and the others to understand the reality of the wider world.
"We want this to be useful to the world as it is today. If the gap is too vast, it won't help anyone, right?"
"I see. It would be a problem if owning one of these became nothing more than a status symbol for the wealthy," Greena said, understanding his intent.
"Exactly. So, for the mass-production model, let's proceed on the assumption that we'll use magi-resin. If we can find high-performance resin, all the better."
Jin pointed them toward their goal.
"But keep in mind, researching high-performance materials on the side isn't a waste of time either."
"I see. I understand now," Rubina said, convinced.
"Alright, let's start the evaluation."
Jin and the girls each pulled up a stool and settled in around the workbench to begin their work.