When Elsa expressed her desire to research Healing and plant magic, Jin nodded in agreement.
"Go ahead and do whatever you want."
"Thank you, Jin-nii."
"It would be great if you could take a look at Planet Hehl's vegetation too, though."
"In that case, I'd like to take Rolona-san along with me."
"Ah..."
Rolona of the All-Creation clan. She was the mother of Sion and Istalis, as well as the foremost plant and agricultural researcher in the Nord Federation.
Unfortunately, she was not a member of the Jin Family.
"If she saw how you look right now, Elsa, she'd definitely be shocked."
"...Mm."
Since they had known each other four hundred years ago and Rolona remembered Elsa from her youth, there was no telling what would happen if they met face-to-face now.
"Anticipating situations like that, maybe we should make some Doppels..."
Jin figured that with them, Reinhard and the others would also be able to visit their descendants.
"I think I'll make both female-type and male-type models. Elsa, will you help me?"
"Mm. If that's what it's for, by all means."
And so, Jin headed to the workshop with Elsa.
To handle the heavy lifting this time, he summoned one Smith unit to assist. After all, he had Mini-Reiko with him instead of Reiko.
Its main role would be carrying heavy metal materials.
Once the materials were gathered, Jin unhurriedly began processing them.
For now, he crafted four female-types and two male-types simultaneously.
Jin rapidly finished their skeletons, muscles, nerves, sensory organs, sub control cores, internal armor, and other components one after another.
He specifically tuned them with a heavy emphasis on magical capabilities.
Elsa proceeded to add skin and hair to the frames.
Ultimately, after consulting with Jin, they made the bodies capable of altering their physique and facial features, just like the Quinta.
"I wonder if this looks good."
"Mm. I intentionally made sure they don't resemble anyone in the Jin Family."
Their skin tone was slightly dark. Since most of their group had fair complexions, this served to differentiate them.
Additionally, their hair and eye colors were set to a common, lighter shade of brown.
"This ought to do it."
"Mm, I'm satisfied."
Both Jin and Elsa were pleased with how they turned out.
These general-purpose Doppels could be operated by Laojun or piloted directly from the cockpit in the laboratory.
Jin thought to himself that he would like Elsa to use one of these sometime soon so they could visit the Nord Federation together.
"Come to think of it, I wonder what Saki is researching?"
When Jin muttered this while taking a break and drinking tea with Elsa at the House, Laojun provided the answer.
"She is conducting research on biological materials."
"Biological materials?"
"Yes. Primarily concerning the carapace of the Gigant Peeder."
"Huh."
The carapace of a Gigant Peeder was the most durable material known, dragon-types aside.
Jin was intrigued as to what she was trying to do with it.
"Thanks for the tea."
Setting down his empty teacup, he said to Elsa, "I'm going to go check on Saki for a bit."
"Mm, have a good trip," she called after him.
With Mini-Reiko perched on his shoulder, Jin set off toward Saki's house.
Ever since her house had been relocated, Saki seemed to prefer working on various projects in her home laboratory rather than the main research laboratory.
"Saki, are you in?"
Popping his head into Saki's laboratory, Jin called out in his usual casual tone.
"Hey there, Jin!"
Saki was conducting some sort of research with Smith 99 as her assistant.
"I heard you were researching biological materials."
When Jin asked, Saki leaned forward eagerly, delighted to discuss her work.
"Yeah, that's right. Look, check this out."
What Saki showed him was a fragment of a Gigant Peeder's carapace.
"The carapace of a Gigant Peeder is weaker than Ancient Dragon hide, but it's a material with a lot of unusual properties."
Back when she was alive... though that was a strange way to put it—three hundred and fifty... four hundred years ago, she had never been able to research it thoroughly enough, Saki explained.
"This is perfect timing. I'd love to hear your opinion, Jin."
Putting down her tools entirely, Saki offered Jin a chair and reseated herself.
"About three hundred and fifty years ago, I was researching why the Gigant Peeder's carapace possessed so much strength. The conclusion I reached back then was that its tissues are arranged in overlapping layers, and mana flows between those layers to enhance the Reinforce effect."
"I see."
As a result, the Reinforce provided by mana was extraordinary, allowing it to boast such immense durability, Saki explained.
"Of course, that's not all. The surface gloss and reflectivity also work to deflect magic that leans toward the physical side."
It was capable of repelling the vast majority of even laser light.
"Its durability operates on a completely different principle compared to Ancient Dragon hide, after all."
"That's certainly true."
Ancient Dragon hide retained a certain degree of flexibility even when reinforced with mana.
The carapace of a Gigant Peeder, on the other hand, became outrageously hard.
"Getting back to the point, if you extract the mana from between those layers—look, just like this."
Saki peeled off a thin sheet from the carapace fragment in her hand to show him.
"This is a sample with the mana completely removed, but you can peel it apart by hand like this. Doesn't it look just like mica?"
"Ah, wow..."
Jin was impressed.
As an aside, Jin's original self—the Jin of four hundred years ago—had actually known this information. It was only the Duplicate Jin who was unaware of it.
Knowing this, Saki was explaining it to him accordingly.
"My conclusion was that by applying Reinforce across these layers, it gains tremendous resistance against forces applied perpendicular to it."
"I see, that makes a lot of sense."
A piece of the secret behind the hardness of the Gigant Peeder's carapace had now become clear.
Jin was reminded of the FRP used in modern Japan.
Fiber-reinforced plastic was a composite material whose strength was improved by embedding durable fibers with high tensile strength, such as glass fiber or carbon fiber, inside plastic.
Plastic had a low modulus of elasticity and low resistance to deformation. Composite materials were created to overcome those weaknesses.
Materials reinforced by mana might share some similarities with this, Jin thought.
Furthermore, there were two main methods for creating composites with such fibrous materials.
One was to evenly disperse finely chopped fibers. The strength of the resulting material had no specific directional bias.
The other was to impregnate plastic with fibers aligned in a single direction. In this case, while the tensile strength along the fiber direction increased significantly, it became weak against tension perpendicular to the fibers.
Seeing the Gigant Peeder's carapace brought this to Jin's mind.
"I want to find an effective processing method and practical applications for this fascinating biological material—this Gigant Peeder carapace."
As it stood, only a limited number of craftsmen could process it.
Moreover, if it were treated so that ordinary craftsmen could work with it, its strength would diminish.
"Hmm, I see... So that's the problem..."
It was quite a difficult challenge, and Jin found himself lost in thought.