The six-ship scouting party spent two full days inspecting the asteroid cluster. They worked through them systematically, moving from the largest bodies to the smallest.
They cataloged roughly two thousand asteroids—a feat of efficiency made possible only by the Peeping Telescope, or "Peeper." Even so, they hadn't managed to check even half of the total population in the belt.
"However, the fact that we haven't detected any mana reactions after investigating this many suggests that there are at least no large-scale facilities in this sector," Laojun reported. "We shall leave the Cepheus behind to maintain a watch. The remaining five ships are to backtrack sixty degrees along the orbital path; that should also be a stable point."
Following Laojun’s instructions, the five remaining ships of the scouting party set off toward their next destination.
As a side note, "backtracking" in this context refers to the direction of the planetary orbit. From a vantage point above the North Pole of Ars, the orbital rotation is counter-clockwise; therefore, "backtracking" denotes clockwise movement.
Furthermore, in terms of Lagrange points, the asteroid cluster had been found at L5 relative to Ars. The point the five ships were now targeting was L4 relative to Hale.
＊ ＊ ＊
"Now then, all that's left is..."
Having received the report on Hourai Island, Jin began a consultation with Laojun.
"Now that we've provided airships to various nations, travel to and from Kunlun Island is a real possibility. We need to be ready for visitors."
"Yes, My Lord. You are referring to the illusion barrier, I assume?" Laojun sensed Jin’s intent immediately. "Please rest assured. Just a short while ago, a more suitable concealment system was completed."
"That's good news."
The illusion barrier was a vital component for keeping Hourai Island hidden from the world.
"The foundation is a barrier that envelops the island," Laojun began. "It is an optical barrier, which remains the same in principle. However, it functions differently from being Invisible."
"Right."
The Invisible effect bends light to show what is behind an object, creating the illusion of transparency. Since it masks visible light, ultraviolet, and infrared, it is virtually impossible to detect with optical instruments. However, it has one major drawback: because light cannot penetrate the barrier, the interior becomes pitch black.
"The optical barrier we developed this time..." Laojun continued his explanation. "...And with this, the area around Hourai Island will appear as nothing but open sea. For these reasons, I believe it is equivalent to the illusion barrier that was once used in the Former Leonard Kingdom."
"I see."
"Next is the passage barrier."
This was a countermeasure for cases where ships or magical beasts might accidentally wander into the island's vicinity.
"We will maintain a weak detection barrier around the island's perimeter. Simultaneously, we will configure the Magi Trans Cannon to construct a teleportation magic circle at a moment's notice."
"Makes sense."
"If a ship or creature makes contact with the detection barrier, we will wake up the teleportation magic circle and send them to the opposite side of the island."
In essence, they would pass right through the island's space without ever knowing it was there.
"The primary difficulty was that velocity normally drops to zero immediately after teleportation. We resolved that by using a force generator in tandem to maintain their momentum."
"But that will require constant, twenty-four-hour monitoring."
"Yes. I can manage it for now with my spare processing capacity, but in the future, I would like you to create a dedicated magi-brain for this purpose."
Jin agreed to Laojun’s request without hesitation. "Understood."
As No. 700672 had pointed out recently, keeping the true extent of Jin’s power hidden was of the utmost importance.
"Thank you, My Lord."
Jin immediately set to work crafting the dedicated magi-brain. Part of him simply couldn't sit still without a project to focus on.
The magi-brain was finished in half a day.
"My Lord, thank you very much," the new entity acknowledged.
"You'll be working under Laojun's direction," Jin said.
"And my name?"
"A name, huh... How about Kagerou?" Jin had briefly considered "Mirage," but he'd decided against it because it didn't have the right ring to it.
"Kagerou? Elusive and ephemeral. It fits perfectly," Laojun remarked.
Thus, Kagerou, the auxiliary magi-brain in charge of the Hourai Island security barriers, was born.
"By the way, Jin-nii."
As Jin was explaining these developments to Elsa, she raised a question.
"I thought the inside of an Invisible barrier was supposed to be pitch black. Why doesn't that happen with this one?"
"Ah, I guess I hadn't explained that part yet. That was the most difficult nut to crack. To begin with, it's not actually an Invisible barrier."
"Eh?"
Initially, Jin had considered various workarounds, such as "creating an artificial sun," "only deploying the barrier when something approaches," or "leaving a small gap for light," but they all had pros and cons that he found unsatisfactory. That was why he had focused on developing an illusion barrier similar to the one from the Former Leonard Kingdom as a superior alternative to basic invisibility.
"Essentially, we see things because reflected light enters our eyes, right?"
"Mm." Elsa nodded.
"So, I thought about it. We just have to process that light."
"Ah, I see."
It was similar to the way image-processing software can remove power lines or other obstructions from a photograph. This new illusion barrier acted as a "special filter." It took the light reflected by the massive object that was Hourai Island and digitally replaced it with light reflecting the surrounding background. The incoming light passed through untouched, while only the outgoing, reflected light was processed.
"Because the incoming light isn't blocked, the interior stays perfectly bright."
"I understand now." Elsa gave him a warm smile.
"On another note," Jin said, turning the question back to her, "you've been heading out quite a bit lately. Is something on your mind?"
Elsa shook her head with a light laugh. "No, it’s nothing like that. The other day, I just went to see Mother to see how she was doing."
The one Elsa called "Mother" in this instance was her foster mother, Marlene. Her biological mother, Mine, was also someone she called "Mother."
"Was she doing well?"
"Mm. It seems Father’s condition is much better too, which was a relief."
"That's good to hear. But you know, you're always welcome to invite me when you go back to visit your family."
At Jin’s words, Elsa replied with a gentle smile. "But right now, Jin-nii, you have so much on your plate."
Jin was touched by Elsa’s consideration. "Thank you," he said softly, shifting closer to her on the seat and gently drawing her into his side.
＊ ＊ ＊
"Now then, there are still many things that need to be done."
Once his break was over, Jin returned to the workshop. With Reiko's assistance, he began making preparations.
"Father, what are you starting on now?" Reiko asked.
Jin answered with a determined smile. "An upgrade to the performance of our aerial combat forces."