The fact that portraits of successive dukes adorned the walls made it easy to infer that this room held great significance for generations of the ducal family.
"Um, would it be better if I stepped outside...?"
Feeling awkward in such a private space, Jin offered to leave, but the Duke shook his head.
"No, I would like you to remain here, Jin-dono."
"...Understood."
Though somewhat hesitant, Jin stayed and took another look around the chamber.
Almost the entire ceiling was covered with Ether Lights (AL), just like the previous rooms, and the stone walls were made of the same material.
Along one wall hung portraits of successive dukes, their duchesses, and several other members of the ducal family.
Opposite them stood a heavy wooden bookshelf lined with a handful of black leather-bound volumes.
What caught Jin's eye even more, however, was a single magi-crystal.
He assumed it was likely an information memory unit.
Meanwhile, the Duke had taken down one of the black leather-bound books, leafing through its pages with evident emotion.
It appeared to be a journal of some kind.
Nanaria stayed close by his side, watching over him gently.
Jin turned his attention back to the Duke and asked about the crystal.
"Your Highness, there is a possibility that information is stored within this magi-crystal. Would you like me to examine it?"
"What was that?"
The Duke stopped turning the pages and looked up at Jin.
"This one right here."
Jin pointed to the magi-crystal resting on the shelf.
"I wonder what could be recorded on it..."
"Well, we won't know without taking a look..." Jin replied, then added, "I can run a brief readout, if you'd like."
"Oh, as expected of you....Please, go ahead."
"Understood."
With the Duke's permission granted, Jin prepared to access the magi-crystal.
"Read."
It was a magi-craft spell originally meant for control cores, but he repurposed it here to extract the stored data.
"...Ohh?!"
"...What a wondrous sight..."
Seeing the faint magic circles and the accompanying stream of characters race by at blinding speed, both the Duke and Nanaria gasped in awe.
(Come to think of it, the last time I used this in front of other people might have been way back in Port Rock Town, when I analyzed that golem that interfered with the race...) Jin mused as the data scrolled past.
In about thirty seconds, the readout was complete.
An ordinary human likely wouldn't have been able to make out a single word, but Reiko—and Laojun, receiving the data stream through her—grasped every last detail without missing a beat.
And while Jin couldn't memorize every single word verbatim, he understood the overall gist.
"...This is..."
Seeing Jin frown slightly, Nanaria asked anxiously:
"Jin-sama, is something wrong?!"
"No, nothing's wrong. The contents were just... not quite what I expected."
"W-What in the world is in there?" the Duke asked, thoroughly intrigued.
Since it wasn't anything that needed to be kept secret, Jin gave a straightforward summary.
"This magi-crystal contains technical documents and blueprints for various magi-devices, Magi Machines, golems, and the like."
Nearly all of it was technology Jin already understood, but measured against this era's standards, more than half of it bordered on out-of-place artifacts.
And compared to the Principality's current level, roughly ninety percent of it would be considered lost, ultra-advanced technology.
When Jin explained this, the Duke offered his own interpretation.
"...In other words, could it be considered a legacy left behind for those of us in the future?"
"Yes, you could certainly look at it that way," Jin agreed.
After all, chronologically speaking, this dated back to when the Magic Federation had begun its rise in eastern Lauren Continent.
It could have been a message intended for this region, which had remained outside the Federation's grasp, or simply a collection of reference materials left behind for posterity.
(Well, things like this are best left to the recipient's interpretation anyway.)
With that in mind, Jin offered a word of advice.
"If you organize and compile these records, I believe they will prove extremely useful to your realm."
"I see..."
The Duke considered Jin's words carefully, his eyes brightening with enthusiasm. "In the near future, I would like to select suitable scholars and entrust the research to them."
"For now, we simply lack the resources and manpower, after all."
For Jin, analyzing and organizing the data on Hourai Island would take less than a day—scarcely half a day, in fact. But he held back from offering, believing it would ultimately benefit the Principality far more if they tackled it through their own efforts.
After thoroughly exploring the Vault and the hidden room, the Duke, Nanaria, Jin, and Reiko returned to the bedchamber above. The Blau Ritter accompanied them, of course.
As for the Blau Ritter itself, they decided that a formal unveiling would take place later, once the Duke had made a full recovery.
The information memory crystal had been returned to its shelf for the time being. The Duke intended to have it analyzed once the Principality's technological foundations had developed a bit further.
"Ah, I am exhausted. My stamina has truly deteriorated."
"Indeed, Your Highness. You must not overexert yourself just yet."
"Yes, I know, Nanaria."
The Duke seemed somewhat embarrassed by his own frailty for tiring after so little exertion, reminded once more of the need to focus on his recuperation.
"Well then, Your Highness, we should be taking our leave soon."
The time was drawing close to four in the afternoon.
"Is that so? It is a pity, but it cannot be helped."
"Indeed. Jin-sama, thank you so very much for everything."
"Truly. Jin-dono, I wish to reward you in some way. Is there anything you desire?...Though our country is not wealthy, so I doubt we can offer anything grand."
The Duke was earnest in his desire to show his gratitude.
Reflecting on his past experiences, Jin replied:
"Well, if possible, I would appreciate a permit or something similar that would let me bypass the tedious entry procedures whenever I visit your country."
Back during his time as the Second Generation, Jin had received titles such as honorary citizen and honorary noble from various nations, granting him open passage into their royal palaces and castles.
He didn't need that level of unrestricted freedom, but he figured it would make life easier if traveling in and out of the realm's cities were a little smoother.
"Understood. I will have the paperwork drawn up immediately. Nanaria, lend me a hand."
"Right away, Your Highness."
Seeing the Duke agree so readily, Jin bowed his head in thanks.
"Thank you very much for granting my request so promptly."
"We will push the paperwork through so that it can be handed to you by tomorrow morning."
With matters settled, Jin and Reiko bid farewell to the reluctant Duke and Nanaria, then returned to the Guest House.