In the end, it wasn't just Reinhard; every member of the Jin Family who was on Hourai Island came over to lend a hand in some way.
Berche, Vivienne, and Milowina gave instructions regarding the interior decoration, while Stearena and Saki adjusted the finer points of the layout.
Everyone was having a wonderful time pitching in.
"Man, when I was little, I remember desperately digging horizontal tunnels into cliffs, calling them our 'secret hideouts.'"
"Rai-nii and Fritz-nii-sama got all muddy and got scolded for it."
"Ah, yeah, that happened too."
In Reinhard's case, it seemed to have been more of a hideaway than a secret base.
"As for me, I always wanted a secret house all to myself," said Stearena as she worked.
"I know what you mean. Kufu, I remember getting scolded for turning the inside of my closet into my own secret room."
Saki also checked the layout dimensions while reminiscing about her childhood.
"I may not know anything about crafting, but I can offer some advice regarding overall layout and how a facility like this needs smooth internal flow, Beena."
"Yes. On the other hand, I'm good at spotting localized defects. Please lend me a hand, Louis-sama."
Beena and Louis looked around the entire area, checking for spots that might have issues.
"Hmm, this dock looks big enough to build large ships in."
"Since we can just use a transporter to deploy them, we could easily launch them straight into the ocean."
Marcia and Rodrigo admired the finished state of the dock.
"I think it would be better to build bulkheads inside the dock, Onii-chan. In that case, having the Adriana in the central area and making smaller compartments around it would probably be better for structural strength, don't you think?"
Hanna was also offering advice to Jin.
"Jin-nii, shouldn't there be a passage for transporting materials, too?"
Elsa proposed creating a direct passage leading from the underground storehouse.
In addition to that:
"If Laojun is going to manage this place, it would probably be better to make it monitorable without having to specifically use Peepers."
"Still, quite a lot of materials can be obtained from the ores excavated while digging underground. This was called rhodochrosite, right?"
"I don't know much about these kinds of structures, but even if people aren't going to live here, I think it'll end up being a rather dry, sterile facility if you don't set aside some living space."
Goose, Toa, and Mine offered advice of their own as well.
Thanks to all their advice and assistance, the underground base was completed just one day later.
＊ ＊ ＊
"Well then, to celebrate the completion of the underground base—cheers!"
"Cheers!"
"Cheeeeers!"
That night, a celebration party for the completion of the underground base was held on Hourai Island.
"Still, to think it was finished in just one day."
"Kufu, that's Jin for you."
"No, it's because everyone helped out, especially with the interior layout and everything."
Jin had thought out the general outline of the base, but he had planned to take his time working on the fine details bit by bit later on.
Instead, everything from the layout to the interior finish had been completely taken care of. What was more, the quality of the finish was so high that there was virtually nothing left to tweak.
"Still, Jin, isn't it not really a base to begin with?" Beena pointed out.
"Well, yeah. It's a hangar, really. Though it has a dock attached to it, too."
An underground hangar, an underground dock. Jin tried to think if there was a better way to refer to it.
"Does anyone have a good name for it?" he asked his companions.
"Hmm, seeing as we already call things the 'laboratory' and the 'submersible base,' wouldn't 'underground hangar' or 'underground dock' be fine?" Reinhard answered first.
"In that case, I think 'underground dock' is good. We'll actually be doing assembly and maintenance there, after all, and it rolls off the tongue nicely."
Marcia offered her opinion, which was somewhat rare for her.
"Yeah, that sounds good."
Since it was Jin's facility, everyone present silently agreed that giving it an overly convoluted name would feel out of place anyway.
"So, are we going to the Shouro Empire tomorrow?" Elsa asked, juice in hand.
"No, tomorrow we'll be building the Blow Floater that can transport Daidara."
"Ah, that's right."
That had originally been the priority.
"We're scheduled to head to the Shouro Empire on the fifteenth, so if we have extra time, we can just relax."
"That makes sense too."
"...Hey, Jin, um... in that Adriana Memorial Hall you're planning to build in the Shouro Empire, are you going to put 'those things' you bought at the auction the other day on display too?" asked Beena.
She was referring to the remnants of the refrigerator, water heater, lighter, popcorn maker, and so on.
They were unmistakably items Beena had crafted under the Craft Queen Workshop brand.
"Yeah. Why not?"
"Uuu... it feels kind of embarrassing."
"There's no reason to be. They're monumental magi-devices."
"A monument to what?"
Reiko chimed in without missing a beat.
"Because they are magi-devices that Father, the Second Generation Magi Craft Meister, was involved with to some degree."
However, Jin partially denied it.
"Well, that might be true, but that's not what I mean."
"From what I can tell, the period when those magi-devices were made coincided with the era when the Kingdom of Egerea's magi-craft... or rather, the entire Allied Kingdoms' level of magi-craft began to rise."
When Jin said that, Reinhard looked at him with slight exasperation.
"Jin... do you realize that the reason it 'rose' was because of your presence?"
"Huh...?"
"Kufu, judging by that face, he had no idea," Saki laughed.
"Jin-nii, do you understand that the turning points of magi-craft in this world were the eras when a Magi Craft Meister existed?"
"Huh...?"
"Haha, Jin really does undervalue himself." Goose chuckled as well.
"It was a turning point precisely because you were there, Jin-kun," Vivienne added with a smile.
"Well, to put it simply, they are positioned as the early magi-devices from the period the Second Generation was active," Reinhard summarized, and Jin finally wore an expression of understanding.
"I-I see."
"Yeah, that's definitely it. Those magi-devices wouldn't have existed without you, Jin."
Beena also insisted that it was thanks to Jin.
"Hmm, looking at it this way, though it's still a ways off, once that memorial hall is built, it might be best if we help choose the exhibits and write the descriptions."
"Agreed."
"Agreed!"
It was the moment the Jin Family reached a unanimous consensus.