"Now then, the reason I've brought you here at this time is..."
Jin finally began to touch upon the heart of the matter.
"It's because I heard that Marcia and Rodrigo-san have independently developed the 'screw'."
"...Did the 'Secret Mobile Unit'—the SP you mentioned earlier—inform you?"
"Yeah, that's right."
Jin nodded.
"Jin-dono, is 'screw' the formal name for the 'submerged waterwheel'?"
Rodrigo immediately latched onto the word.
"It's not so much a formal name as... what it was called in the world I came from. Its shape looks like this."
At Jin's signal to Laojun, a diagram was projected onto the magi-screen at the front of the room.
It depicted screw propellers used on modern Earth, showing variations with two, three, four, five, and six blades.
"Oh, this is...!"
Rodrigo gasped.
"In the world I lived in, these kinds of designs were common."
The four-bladed version was nearly identical to the one Rodrigo and his team had developed. If there was any difference, it was only that Rodrigo's version had a thicker shaft and the curves of the blades weren't quite as smooth.
"I see. So, Jin-dono, the thing I most want to ask is... no, I'll stop myself."
However, Jin had a vague idea of what was on the man's mind. He decided to ask aloud.
"...By any chance, are you struggling with how to prevent water from leaking along the screw shaft?"
"H-How did you know that?"
It was a direct hit.
Jin himself had been plagued by that very problem during his days of building motorized model ships.
Most of the model-use screws Jin had used had a two-millimeter shaft. Since they were simply passed through a pipe with an outer diameter of three millimeters and an inner diameter of 2.4 millimeters, the gap was quite significant.
He had also built plastic models of submarines. At the time, the structure involved creating a grease trap inside the hull for the screw shaft to pass through. He recalled how difficult it had been because if the grease leaked onto the hull, the adhesive wouldn't stick properly.
The component was known as a 'stern tube', and while various seal structures had been devised on Earth, Jin wasn't familiar with the highly technical details.
Thus, he answered simply.
"Because I've struggled with the same thing before."
Marcia and Rodrigo both widened their eyes in perfect unison.
"Wait, you too, Jin?"
"Jin-dono has?"
Seeing how similar their expressions were, Jin couldn't help but think that they were definitely father and daughter. He then offered one of the solutions he had used.
"One way is to extend the shaft and bring the opening of the pipe above the waterline."
Basically, water shouldn't be able to enter if the opening was above the surface of the water outside the ship. This was particularly effective for light models.
"I see!"
"There are other methods, of course, but it seems Rodrigo-san wants to complete his invention without being told all the answers."
Having said that, Jin actually wasn't entirely sure how full-sized modern ships handled it either. None of the vessels currently on Hourai Island utilized screws, after all.
"No, no, hearing just that is more than enough."
Rodrigo nodded with a look of satisfaction. Jin had no intention of teaching them everything from start to finish. He felt it was enough to offer support for their own efforts.
"Well then, let's leave the heavy talk at that for tonight. The timing seems right, so shall we have dinner?"
It was nearly 8:00 PM Hourai Island Time. Jin and Elsa were both feeling quite hungry. On the other hand, for Reinhard, Saki, and the others from the Shouro Empire, only about an hour had passed since lunch.
"Jin, I think we'll head back and come again tomorrow."
"Yeah, that's probably for the best."
With that, Reinhard, Saki, Toa, and Stearena returned to the Shouro Empire for the night.
"...Sigh. So this is Jin's true capability. Just as I thought, it's truly incredible."
Marcia spoke in a deeply moved tone as they moved from the basement command room to the dining room on the first floor.
"I feel like I'm finally realizing just how lucky I was to have met you back then, Jin."
At the dinner table.
"This is delicious!"
"I believe you called it 'white rice'. I never knew such a delicious thing existed."
Marcia had clearly taken a liking to the rice. Rodrigo had apparently tasted rice before in the Shouro Empire, but it had been unpolished brown rice, leaving him astonished by the flavor of the white rice.
"This soup goes great with it, too! The ingredients are unusual, but it's wonderful."
It was miso soup with tofu and aburaage, and Marcia seemed to love it.
"And these pickles...? They don't taste like they were pickled in vinegar, but they have a unique, delightful flavor."
Rodrigo shared his thoughts while crunching on nukazuke made from a vegetable similar to cucumbers. Finally, they finished with a cup of hojicha.
"Mmm... even without sugar, there's a faint sweetness, a bit of astringency, and such a wonderful roasted aroma. I'm a fan!"
"Exactly. The taste of home, Kuhe, is good in its own way, but this kind of simple flavor is truly exceptional."
While offering commentary like professional food critics, Marcia and Rodrigo savored their tea. Jin felt a wave of relief seeing them enjoy the Japanese cuisine.
"Haha, I'm glad you liked it. Well, for tonight, I'll have you soak in the hot springs and get some rest. Once it gets light tomorrow, there are many more things I want to show you."
In the bathroom.
"Whoa, this isn't just hot water! It feels amazing!"
"..."
Sharing the bath with her, Elsa felt overwhelmed by the physical difference between herself and Marcia, even though she had already known the truth.
"Jin-dono, you called this a 'hot spring'? To think such water wells up from deep underground!"
Rodrigo was relaxing in the tub with a towel balanced on his head, looking like a typical middle-aged man enjoying his soak.
In the bedroom.
"Mmm, sleeping on the floor is certainly a novel concept. It shows just how clean the floor is!"
"And these fluffy futons... the material is magnificent."
The two of them seemed to take an immediate liking to the tatami-matted room and the magisilk futons.
"Your Majesty, regarding a shop in the castle town called the Raglann Company..."
In the Klein Kingdom, discussions regarding the gift for the Celuroa Kingdom's Founding Anniversary Ceremony were still dragging on.
"The Raglann Company?"
"Yes. It is an emerging merchant company that has grown significantly over the last year or two. Apparently, they conduct trade with Kaina Village."
The report came from Jackson Red Bados, the Minister of Industry, who had stepped into the vacancy left by the treasonous Delite Domus Hanks.
"What was that?"
The one who shouted was Clarot Bados Keris, the Minister of Magic.
"Kaina Village... isn't that the village where the Lord of Kunlun, Lord Jin Nidou, resides?"
"That is correct. It seems that company has been associated with Lord Jin Nidou since he was still a commoner, and they handle the tools and magic tools he creates on a nearly exclusive basis."
"Exclusively, you say..."
The Minister of Magic was about to say more, but Chancellor Powell Danner Hudson interjected first.
"Avoid the folly of trying to ban their exclusivity or complaining about their favorable treatment. Do not repeat the mistakes of that Earl Walter."
"I—I understand."
"Furthermore," Minister of Industry Jackson Red Bados continued.
"My own investigation has revealed that they carry original products such as metal pens, rubber balls, and magi-stoves. In fact, most of you are already using these metal pens."
"Oh? So these pens were obtained from there?"
Metal pens had become common even within the Royal Castle, but it seemed no one had concerned themselves with how they were sourced.
"...If I may be so bold, I would like everyone to pay more attention to such changes in daily life, even if they appear trivial."
The Minister of Industry was indirectly scolding them for their lack of awareness. At thirty-six, he was young for a cabinet minister, but he wasn't afraid to speak his mind.
"...Umu. If it is the work of Lord Jin Nidou, it is certain that the Celuroa Kingdom will not have seen them. Let us list the metal pen as a candidate."
"...It might seem a bit underwhelming as a state gift, though," the Minister of Magic muttered. They were undoubtedly convenient, but he questioned if they were prestigious enough for a gift between nations.
"We have little time. These appear to be made of bronze, but perhaps we could have them crafted from silver, gold, or mithril?" the Chancellor suggested.
King Alois III could only nod in agreement.
"Umu... but with only ten days remaining, a special order would likely be difficult. That is the pity of it."
"In that case..."
"If we require the work of Lord Jin Nidou, how about one of the Universal Golems?"
They had originally commissioned twenty units, but ten had been lost during the crisis at the Inado Mine when the Gigant Peeders appeared. Only ten remained.
"Umu... Indeed, those would certainly hold their own against any golem made in the Celuroa Kingdom, but..."
Seeing the King's reluctance to part with them, Fadas Lofus Fairgram, the Minister of Defense, finally spoke up.
"If I may be so bold, Your Majesty. Regarding Princess Lieschen... she has an automata of excellent quality, though perhaps not an ancient artifact, yes?"
"Oh, yes, I remember her. The automata who served as Lieschen's nurse—Tia, I believe."
"How about we send her as a gift?"