By treating Duke Gilberto de Darato, Jin's popularity rose even further.
At the same time, the credibility of the World Conference skyrocketed.
Thanks to this, they were able to conclude a provisional agreement with terms identical to those of the Mimaka Principality without a hitch.
"I would like to stay for one more day so I can check on the condition of His Highness the Duke."
Manon made this proposal to Chief Envoy Marquis Theobald Theoderic von Grain.
"Mm, that should be fine. We scheduled buffer days in anticipation of prolonged treaty negotiations, after all."
"Thank you very much."
"No, the thanks belong to you. Truth be told, concluding the agreement faster than anticipated is all thanks to Manon-dono and Jin-dono."
Here, Marquis Theoderic glanced around the guest room and noticed that Jin and Reiko were absent.
"Yes. Jin-sama is currently with His Highness the Duke."
Upon Manon's explanation, Marquis Theoderic nodded in understanding.
"I see. In that case, I will do what I can on my end as well."
He was scheduled to discuss tax rates with the minister of general affairs shortly.
Offering advice at this personal level would surely prove beneficial for future relations between their nations.
After lunch, Jin was in the Duke's bedchamber in the inner palace alongside Reiko.
"Jin-sama, I apologize for summoning you here."
The one who bowed her head and said this was the Duke's fiancée, Nanaria.
"I asked him to come because I wished to see him."
Duke Gilberto de Darato stood up for Nanaria.
"First and foremost, allow me to thank you once again for yesterday....Today, I feel even better. I feel as though I could already walk around."
"Though Nanaria strictly forbids it," the Duke added with a chuckle.
And that same Nanaria said,
"It feels like a dream that the day would come when Jil-sama could make such an expression."
Immediately after saying this, a look of dismay washed over her face.
"A-Ah, Your Highness, please forgive me!"
She seemed to be apologizing for calling him "Jil-sama" in front of company.
"...Well, I'm not a noble, nor do I belong to any specific country, so please don't mind me."
Jin offered this consolation, unsure if it served as a proper follow-up.
However, the nature of his words surprised the Duke.
"What!...Jin-dono is a free man, then. I truly envy you."
"Yes, I suppose I was just lucky."
He had been chosen as the Second Generation Magi Craft Meister simply because he possessed the same magic pattern as the First Generation.
While it was hardly something that could be brushed off as mere luck, Jin let it stand at that.
"...To such a Jin-dono—no, precisely because it is you, Jin-dono—there is something I would like you to see."
"What might that be?"
"Nana, bring that here."
"Yes, Your Highness."
The Duke was also calling Nanaria "Nana," but Jin pretended not to hear.
Then, Nanaria brought over a single box.
It was ornate, decorated like a jewelry box, and stood roughly the size of a tissue box.
"This box has been passed down through generations of the ducal family, but it has no keyhole or anything of the sort, and it simply will not open. If it is you, Jin-dono, do you think you could open it?"
"May I take a look at it?"
"Of course. Please, go ahead."
With that, Jin received the box from Nanaria.
"It's fairly heavy."
Jin estimated that it was made entirely of metal.
"There's no... keyhole, indeed."
Jin inspected the bottom as well.
"The creator is... D. E. M....?!"
(Deus Ex Machina?!)
That meant it was a box created by Jin four hundred years ago under the name of Maquina.
(If that's the case, then surely...)
Jin examined the box closely once more.
"I see."
Jin twisted the rose-patterned ornament set in the center of the top surface and slid it across.
Next, he slid the metal fittings at both ends of the top toward himself.
"Oh?!"
"Such a mechanism was hidden there...?!"
Watching this, the Duke and Nanaria let out gasps of astonishment.
In short, just like Hakone puzzle boxes, this box had a trick mechanism built into it that prevented it from opening unless a specific sequence of steps was executed.
From there, Jin continued manipulating the mechanism, completing a total of twenty operations.
"It should open now."
He then handed it straight back to the Duke.
"Oh, truly?"
The Duke gently rested his hands on the lid and applied pressure.
Then, without a sound, the lid lifted away.
"It opened!"
Nanaria, who was watching from the side, cried out.
"It opened! It really opened! Jin-dono, I cannot thank you enough!!"
Resting inside were two keys—one gold, and one silver.
"This is it...!"
They seemed to be rather important keys, Jin thought.
"These are said to be the keys that open the ducal family's Vault."
Is that so? Jin felt a flicker of curiosity.
"On top of that, this was a memento of my grandfather, so I am truly glad to have the box opened like this."
It appeared that the procedure for opening it had been lost during the Duke's father's generation.
"Ah, so that was the case....Shall I write down the steps to open it?"
Jin offered.
"Yes, please... I would be most grateful."
"Understood."
Jin borrowed writing utensils and smoothly jotted down the steps.
Since it was something he had made in the past, the steps were completely clear in his head once he unlocked it.
Having finished drawing an illustrated instruction sheet in about five minutes, Jin said,
"Please burn or discard this once you have memorized it,"
and handed it to the Duke.
"Thank you very much, Jin-dono."
"...Now then, are you interested in knowing what lies dormant inside the Vault?"
The Duke was already addressing Jin with polite, respectful deference.
"Well, it would be a lie to say I'm not."
"I thought as much."
The Duke smiled warmly.
"...Actually, the door to the Vault is right here in this room."