In a rare turn of events, Jin found himself with time on his hands on Hourai Island in the year 3900 of the Continental Calendar.
Since Jin was the type of person who was always either crafting something or getting caught up in trouble whenever he had a spare moment, such idleness was truly a rarity.
The date was April 4th. Spring was in full bloom, and the weather had a pleasant warmth that invited drowsiness.
"I know. I'll try making that thing I've always regretted not having."
Jin decided that now, while he had the leeway, he would tackle a project that had been on his mind but had remained sidelined due to its lower priority.
It was a counterpart to the Peeper—an eavesdropping device, so to speak.
As things stood, while the Peeper allowed him to see distant locations, he couldn't hear any sounds, including voices. Laojun compensated for this by using lip-reading, but even that had its limits. It was useless if the target's face wasn't visible.
"I wonder if there's a better way..." Jin pondered in the laboratory workshop.
"Sound is just the vibration of air. In other words, it's a physical vibration. I just need a way to pick that up."
There was already a magi-device called a magic ear. It functioned much like a wireless microphone. The component that picked up sound utilized a physical structure: a thinly formed magi-crystal served as a diaphragm, converting sound into magi much like a dynamic microphone.
"If I could create a diaphragm out of magi..."
That was the conclusion Jin reached.
Incidentally, even on modern Earth, there was such a thing as a laser listener. This worked by aiming a laser beam at the window glass of a room one wished to monitor and measuring the reflected waves. Since the glass vibrates due to sound waves, the returning laser beam carries those vibrations with it.
That was the rough explanation, at least. Jin had heard of the principle and had considered using it before, but he had abandoned the idea due to its drawbacks: it was only effective if the target was inside a room, and it wouldn't work on materials that absorbed sound waves, such as mud walls.
Jin spent two days working out the details for a new method. He managed to replace the physical diaphragm by applying the principles of a physical barrier (solid barrier). He maintained an invisible barrier with invisible magi and used its vibrations to modulate a carrier wave—specifically, an ether wave.
"Yeah, this looks like it'll work."
The main challenge was the strength of the solid barrier acting as the diaphragm. If it was too strong, it wouldn't vibrate, making it impossible to hear anything. Conversely, if it was too weak, the signal would be drowned out by noise, and he wouldn't be able to pick up the essential audio.
"The sensitivity will also change depending on where the diaphragm is installed..."
So, Jin decided to make the strength of the diaphragm adjustable—effectively, a form of tuning. By weakening or strengthening it, he could adjust it to a level where the sound could be heard clearly.
『This will be perfectly functional.』
Since Laojun would handle the operation, including the tuning, Jin felt at ease. This technology was dubbed the Magi-mic, and it allowed Laojun to gather information from around the world even more effectively than before.
"With this, your intelligence gathering should be much easier, Laojun."
『Yes, My Lord. Thank you very much.』
Jin was relaxing at the House, drinking tea. Reiko was serving him.
『Being able to pick up audio along with visual information is a significant advantage in intelligence operations.』
"I imagine so."
『Furthermore, it is advantageous that audio does not require as much precision as visual data.』
"I see, that makes sense."
In the case of visuals, the image would blur if the sensor wasn't fixed firmly, but for audio, a lack of stability merely meant an increase in noise, which could usually be compensated for through adjustment. Since visual information wasn't strictly necessary for eavesdropping on things like meeting contents, this technology would likely be indispensable from now on.
"By the way, how are things going over on Hale?"
『Yes, My Lord. To put it simply, everything is proceeding smoothly.』
"That's good news."
Jin nodded while sipping his hojicha.
『The greening process is the most advanced. We are raising seedlings of the native plants and transplanting them across various regions.』
"And the measures against the aridity?"
『Yes. Perhaps because the seawater has returned to its original level, the atmospheric humidity is gradually increasing, and precipitation is rising as well. I believe a forest will form there in the near future.』
Jin smiled wryly to himself, knowing that Laojun's idea of the "near future" likely spanned centuries.
(Come to think of it, I remember hearing that the Fuji Sea of Trees was a forest born from an eruption just over a millennium ago.)
To be precise, it was approximately 1,200 years ago, in the 6th year of Jogan (864 AD). There were other examples of landscapes in modern Japan that were surprisingly recent in the grand scheme of history.
The tourist spot Onioshidashi, which spreads at the foot of Mount Asama on the border of Nagano and Gunma, was formed in the 3rd year of Tenmei (1783). Similarly, the group of lakes and marshes scattered at the foot of Mount Bandai, including Lake Hibara, were born from an eruption and explosion in 1888, during the mid-Meiji period.
(The Orphanage Director used to point out that the scenery was all wrong every time Mount Bandai appeared in a period drama.)
The Orphanage Director at the facility where Jin grew up loved period dramas, but she was also a stickler for historical accuracy. For example, she would point out that during the time of Mito Komon, Zenko-ji in Shinano had burned down and only had a temporary main hall, or that inns weren't nearly as well-established in that era as they were depicted.
Yet, despite her nitpicking, she truly enjoyed every period drama she watched.
(Looking back, maybe that was her way of trying to spark my interest in history.)
It was only now that Jin truly realized it.
Anyway, it was heartening to hear that the development of Planet Hale was going well.
"No. 700672... the 'Elder' seems fully intent on settling down there, too."
Then Jin turned his thoughts to a problem that had yet to be resolved.
"Marikka's homunculus... huh."
By their nature, servants like No. 700672 required a Master—a spiritual pillar or a source of emotional stability. When Marikka eventually passed away, No. 700672 would surely be tormented by Master Loss Syndrome. Jin desperately wanted to avoid that.
For some reason, neither Laojun nor Reiko would give him any clear advice regarding this matter.
(Maybe they're projecting their own relationship with me onto them...)
When he looked at it that way, Jin felt he understood their feelings, which prevented him from pressing them too hard.
(Should I at least make preparations for when the time comes...?)
But if he did that, Jin felt he would want to prepare something for Sion's sake as well.
(Is this just me being selfish again...?)
Jin was now a Duplicate, and likely an immortal one at that. This meant he would have to watch many friends and acquaintances pass away in the years to come.
(It's not like I chose to be this way.)
Things were fine for now, but the thought of the partings he would inevitably experience left him with an indescribable heaviness in his heart.
Perhaps sensing Jin's mood, Reiko approached him with the teapot. As she poured his tea, she spoke softly.
"Father, I am here. So is Laojun, and so are my brothers and sisters."
"...Thank you, Reiko."
Jin was grateful for her concern. Thinking back, Reiko had endured a thousand years of solitude while searching for the Predecessor's successor, and after the human Jin had passed away three hundred years ago, she had waited once more until the current Duplicate appeared. It was no exaggeration to say she understood loneliness better than anyone.
"You are the one who can change even fate, Father."
"Haha, thanks."
Jin truly hoped he could live up to that as he finished his tea.