Marcosius of the Frenzy clan.
An engineer hailed as the greatest genius since the clan's inception, he had once operated in the shadows across the Allied Kingdoms.
He had manipulated a man named Marcus, instigated Elsa's father, and even attempted to poison Saki's grandfather, Marquis Gehren Teoderik von Eisen, with arsenic-laced wine...
Throughout that time, he had harbored a bitter grudge after the golem he crafted proved to be completely outmatched by Reiko.
However, during the "Failure" incident, when Jin and Reiko saved the Northern People—then referred to as the demon race—his grudge had dissolved.
Yet his ambition to build a golem or automata capable of surpassing Reiko never vanished. Once peace returned to the Nord Federation, he vanished, and his whereabouts had remained unknown ever since.
"...I wonder if that Marcosius took on disciples?"
Since Laojun had reported that both San Marco and Marukonen were Lauren Continentals, Jin deduced they were unlikely to be his children or grandchildren.
"Judging from what you've told me, that seems quite likely."
"I see..."
As Jin and Lordtoss discussed the matter, Rubina chimed in eagerly.
"Hey, hey, what does that mean? Tell me too!"
"Ah, sorry, sorry. Well, it happened a long time ago, but..."
Jin gave Rubina a brief summary of his past connection with Marcosius, taking care to gloss over the darker misdeeds the man had committed.
"So that's what happened in the past..."
Although Rubina had learned the general history of the Nord Federation, she had never been taught the finer details. Or rather, such matters were intentionally omitted from standard lessons.
"Yeah. That's why I suspect they might be his disciples. From what I hear, their engineering system is a bit unusual."
This was information gathered through Elena.
She had mentioned noticing several subtle deviations from the lineage established by Adriana Barbora Tsetse.
"If the opportunity arises, I'd almost like to meet him."
Since they were a long-lived race, Marcosius himself might still be alive.
Jin couldn't help but wonder what the man would think if he saw the Reiko of today, refined and improved far beyond what she had been back then.
"Well then, moving on."
Having finished his tea, Jin shifted gears.
"Aren't we going to fly them?" Rubina asked.
"Yeah, but before that, there's just one thing I wanted to bring up," Jin replied. "As we move forward with this kind of development, I was thinking it might be a good idea to start conducting wind tunnel experiments."
The concept involved blowing air through a large enclosure to test scaled-down models or full-sized components.
"By doing that, we can cut down on the effort and danger involved in building and flight-testing actual full-scale machines."
"Ah, that's a wonderful idea."
"That sounds much better than just building models and tossing them into the air."
Both of them grasped the purpose and value of the proposal immediately.
"So, we'll build a pilot wind tunnel here in Toka Village first. Eventually, we can hand over ownership to the village. As the first wind tunnel on Planet Ars, it'll draw users, and it might even turn into a landmark tourist attraction."
"I see. You've really thought this through."
"It'll be great for the village, too."
Seeing that neither of them had any objections, Jin decided he would discuss the plan with the Village Chief later.
"Well then, before that, it's time for our test flights."
All three of them shared the same eagerness to take turns flying the custom Delta X02 variations they had each built.
"Whoa! This is so easy to fly!"
"Hmm, it feels remarkably stable."
"This is...! It's going to take some time to really master this one."
Rubina took Jin's craft up, Jin flew Lordtoss's, and Lordtoss took Rubina's for a spin.
Through this first round of flights, they each gained a clear sense of the crafts' individual characteristics.
Then they swapped once more.
"It's stable, but... how should I put it? Sluggish?"
"Yeah, this really is a wild horse."
"Such delightfully responsive handling..."
With Rubina trying Lordtoss's craft, Jin testing Rubina's, and Lordtoss piloting Jin's, the differences between all three designs became crystal clear.
"...All right, let's share our thoughts."
"Okay!"
It might seem tedious, but for an engineer, reevaluating an existing design through hands-on experience was crucial.
Jin wanted Rubina to learn that firsthand.
"Regarding the 'tuning' you mentioned earlier, Jin-san, I feel the term fits perfectly," Lordtoss said, opening the discussion.
Rubina nodded in agreement. "Me too, me too! Though I did feel my own tuning might've been a little too extreme."
"You think so? As for mine, I felt it ended up being pretty Mild in the end."
Having experienced both Rubina's and Lordtoss's machines, Jin felt his own craft was, to put it kindly, well-behaved like an honor student, or to put it bluntly, lacking distinct flavor.
"I don't think that's true at all. Though mine was definitely on the wild side," Rubina countered.
Jin could tell that flying each other's machines had introduced a healthy dose of self-reflection and doubt into their perspectives.
"Even so, it's fascinating how much the feel can change purely through tuning," Lordtoss observed with genuine admiration.
"Isn't it? And all within a scope that hardly even qualifies as a major modification."
Though a few optional parts had been attached, at a glance they appeared to be identical models.
To a trained eye, of course, the distinctions were vast...
"Right. If we identify and extract the exact elements needed to bring out the characteristics of these three crafts, and design them so they can be reproduced simply by swapping optional parts, commercial distribution to the general public becomes much more feasible."
In essence, it was the same philosophy used for optional packages and trim levels on passenger vehicles in modern Japan.
"Does that mean you're working on the assumption that these will be sold eventually?"
"Eventually, yes."
There were still plenty of hurdles to clear, including production costs and licensing systems.
He had no intention of selling them immediately, nor would Jin be selling them directly.
"Sales would likely be handled by Avalon or Nostalgia."
The structure would be simple: manufacturing on Hourai Island, sales through Avalon or Nostalgia.
"It might also be worth setting up a maintenance workshop in Toka Village. A licensing center, too."
If a licensing system were introduced, practical exams would be mandatory. Hosting those here in Toka Village would provide a steady boost to the local economy, or so Jin reasoned.
"You really consider every angle, Jin-sama."
"Well, naturally."
"However, if Toka Village develops too rapidly on its own, wouldn't that draw resentment from the neighboring towns and villages?" Lordtoss asked, offering a measured perspective.
"That's a fair point. In that case, it might be wise to distribute roles to Rakuno Village, Doppa Village, and the Town of Charles as well."
In the end, Jin concluded, those broader administrative decisions were up to the Klein Kingdom to make.