The following day, the 24th, Jin and Reinhard sequestered themselves in the workshop as soon as they finished breakfast.
Saki, who had stayed overnight at the estate, joined them, and this time Berche came along as well.
"Alright, let's start with the skeleton."
After dinner the previous night, Jin and Reinhard had consulted one another and hammered out the general specifications for the new automata.
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"What do you think about an androgynous design?"
"You mean someone who could pass for either a man or a woman?"
"Yeah, exactly. Besides, I'm not sure how much sense it makes to give an automata a distinct gender anyway."
When Jin said that, he failed to notice that Reiko, standing behind him, looked a bit forlorn for a moment.
"That said, the base will be male-pattern, right?"
"That's right. We'll just give them a slender build and let the hair grow a bit longer."
"I see, I see."
"For instance, they can usually work as a butler, but if the situation calls for it, they can dress as a woman and serve as a maid."
"I see! That’s brilliant! A multi-purpose unit!"
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"Light silver would be best for the skeleton."
The moment Jin made the suggestion, Saki spoke up in shock.
"What?! Reinhard, light silver runs two million Toll a kilo!"
Spoken like a true alchemist; she was well-versed in the market rates for premium materials, even if she lacked any semblance of personal financial sense.
"Oh, it's fine. Jin donated it."
"Donated...?"
"I'll explain everything eventually. If you're going to keep company with Jin, Saki, you have to let go of your preconceived notions."
Reinhard told her this with a chuckle, but Saki remained silent with her head bowed for a full minute, struggling to digest the information. Finally, she looked up.
"...Kufufu, I get it, Reinhard. You win. An alchemist's creed is that one cannot make new discoveries if they are bound by the world's common sense. I’m truly embarrassed."
She accepted the reality with a surprisingly refreshed expression.
Berche didn't look particularly surprised, perhaps because her own understanding of economics was thin, or perhaps she simply lacked knowledge regarding rare materials.
With the distractions out of the way, they resumed their work.
The height was set at 160 centimeters—roughly the same as Jin, and only slightly taller than Saki. The target weight for the slender physique was 50 kilograms.
"First, the skeleton. I've been mulling over several ideas after watching you build your golems, Jin."
Saying that, Reinhard produced the block of light silver. In truth, Jin had arranged for it to be brought from Hourai Island in the middle of the night.
Reinhard began to shape it. Jin had collaborated with Reinhard several times now, but this was the first time he had seen him apply Craft Magic with such intensity.
Reinhard was remarkably skilled; his claim that he’d been studying Jin’s techniques was clearly no idle boast. The basic skeleton was finished in about fifteen minutes.
"How is it, Jin? I’d like your thoughts."
In response to Reinhard's question, Jin gave his candid assessment.
"It's impressive, Reinhard. To think you could produce something like this after just a glance at my work! If I had to nitpick, I'd look at the fingers and wrists. We call these ball joints, but the movement looks a bit sluggish."
After offering his critique, Jin decided it was his turn to contribute. He took a small lump of adamantite and performed fine adjustments, coating the joint sections as he went.
"I see! So you're reducing joint wear while simultaneously making the movement more fluid. This is very educational."
At that point, Saki, who could no longer sit by as a silent observer, chimed in.
"I hate to interrupt while you two are so focused, but let me ask... is that based on a human skeleton?"
Jin was the one who answered.
"Yeah, that's right. An automata is designed to mimic a human. If that's the case, why wouldn't you start by making the skeleton as accurate as possible?"
"Hmm," Saki hummed, leaning in to carefully examine the skeleton lying on the workbench. "The ribs and pelvis have been simplified... Sorry for the interruption. Please, continue."
Next, Jin took the lead. He began to arrange the magical muscles made of magical fiber.
As he installed the musculature in the proper order, Jin found himself wondering how the Predecessor had obtained such deep knowledge of anatomy.
Meanwhile, Reinhard and Saki watched Jin’s hands with rapt attention. Only Berche looked a bit lost, unable to follow the technical complexity.
"Finished."
The installation of the muscles took about five minutes. For Jin, this was a rather leisurely pace.
"Wow, Jin, that was a fantastic reference! Thanks!" Reinhard said excitedly, slapping Jin on the shoulder.
"Jin, I've learned a great deal today," Saki added with a quiet, respectful nod.
After that, they wired the magi-nerves with mithril and prepared the control core.
Reinhard mentioned that it might be overkill now, but since Jin knew the threat the demon race posed, he insisted on giving the core a shield structure just in case.
"Now then, it's finally time to place the tactile sensors!"
Reinhard sounded genuinely delighted. Jin felt the same way.
"Kufufu, we're finally going to install a world-first function, aren't we?" Saki added, her face full of anticipation. Only Berche maintained a confused expression.
They had forty pre-made tactile sensors ready. They distributed them across the body: two in each palm and two in each sole, accounting for eight locations across the hands and feet. Then they placed five on the chest and stomach, three on the back, and two on the buttocks for a total of ten points.
Using multiple sensors ensured that functionality wouldn't drop significantly if one were damaged, and it also allowed the core to triangulate the center of a stimulus based on the varying signal strengths from each sensor.
They placed four on each arm and leg for a total of sixteen points. Finally, they placed five on the head, completing the primary layout.
"Hmm, there's one left over. Should we keep it as a spare?" Jin asked.
Saki made a suggestion. "Since this is partially an experiment, why don't we use them all? What about inside the mouth?"
"Hmm, I see. For sensing when they bite something. That could be useful."
With that, all forty tactile sensors were installed.
These sensors would relay information to a dedicated sub-control core, which would organize the data before passing it to the main control core. This would reduce the processing burden on the main core while allowing for far more delicate physical control.
"Reiko, use Trace and Inspection to monitor the flow of mana. Reinhard and I will test each of the sensors."
"Yes, Father."
Precision monitoring was one of Reiko's specialties.
Jin and Reinhard applied stimuli to the sensors—sometimes simultaneously, sometimes individually—and tracked how the resulting mana signals were transmitted to the sub-control core and processed.
They spent two hours on this tedious verification. Once they were satisfied with the results, they prepared to move on to the next phase.
"Everyone, it's nearly noon. Please take a break and have some lunch."
Berche, who had been waiting patiently, spoke up after checking the sundial in the garden.
"Oh, is it that time already?"
"Time really flies when you're absorbed in your work."
"Kufufu, I couldn't agree more."
The three like-minded engineers each shared their thoughts as they set down their tools.
"Berche, I'm sorry. I feel terrible for leaving you bored all morning."
After washing his hands, Reinhard went over and gently put his arm around Berche's shoulder.
"...Oh, honestly, Lord Reinhard. When you say things like that, I can't possibly stay cross with you!"
Berche, who had looked a bit put out moments ago, rested her head on his shoulder with a small smile.
Watching the two of them, Jin and Saki could only manage wry grins.
"...Well, that was quite the 'treat' for us onlookers," Saki joked.
"Yeah. It’s certainly a beautiful thing to see people so close," Jin added.
Saki and Jin shared a look, both of them content to see their friends so happy.
Eventually, Reinhard realized they were being watched and sheepishly pulled his hand away. Berche also came to her senses, her face turning a deep shade of crimson as she saw Jin and Saki smiling at them.
"L-L-Lord Reinhard, let us go to the dining room!"
"Ah, right. Yes, Bell....Jin, Saki. Let's go eat."
Muttering to hide his embarrassment, Reinhard gestured for Jin and Saki to follow as he led the way toward the main house.