How could he get Laojun to notice his presence? Jin pondered the problem.
"Is the solid barrier deployed underwater as well?"
He spoke the thought aloud, but the answer was already within him.
"It isn’t active within solid earth, but it should be present in fluid water..."
It went without saying for the air, which was a gas.
"And a magic barrier would likely extend into solids too. It wouldn't make sense otherwise if the goal was to block earth-attribute magic."
"Hmm."
He had been considering traveling through the water in the Pegasus 2 and landing at Tatsumi Bay, but that seemed difficult.
"But the general direction of the idea isn't bad."
If he identified the problems with the execution and prepared countermeasures, then perhaps... Jin thought.
"The illusion barrier doesn't exist deep underwater, and it doesn't actually block movement anyway."
"Yes."
"In that case, the first hurdle is the solid barrier. We should be able to bypass it by tunneling through the earth beneath the seabed."
"That is correct, Father."
From Reiko’s response, Jin realized that his reasoning was correct.
"As for the magic barrier, if we deploy our own magic barrier, there will be no interference."
"Yes."
So far, so good. The problem started from here.
"Regarding the nitrogen, we can just wear space suits."
"That should be fine then."
"The ether eliminator and the Magic Canceller barrier. Those are the problems. However..."
Jin glanced at Reiko.
"Humans are immune to them."
At those words, Reiko seemed to feel a significant shock.
"Father..."
"That's how it is, right, Reiko? It has to be me who goes, doesn't it?"
"..."
Her silence was an affirmation.
"Alright."
Jin gave a firm nod, his course of action decided, and began to think about what would be necessary to achieve it.
"A craft capable of moving through the seabed’s soil or rock, huh."
That would be the biggest bottleneck. Such a thing shouldn't exist in the current world.
"A 'Mole,' then..."
Yes, except on Hourai Island.
"They probably have them there, but since there isn't one here, I'll have to build it."
"I—I will do whatever I can to help!" Marikka spoke up with great enthusiasm.
"Thank you. I'll need you to share some metal materials with me."
"Please, take as much as you need."
"Reiko, help me....You too, Hope."
Prioritizing the construction of the means for his return, Jin decided to have Hope—who had been monitoring the Watcher—assist them for a while.
"Understood."
Thus, Jin began building a "Mole" as the means to reach Hourai Island.
A "Mole" was a cylindrical Magi Machine specialized for digging through the ground. The tip of the cylinder was equipped with adamantite blades, which would pulverize the bedrock in its path. The pulverized rock debris would then be sent outside using a Warp Gate. It could also proceed while filling the hole behind it by sending the debris to its rear.
Using such a Mole as a base, Jin intended to create an Underground Vehicle that he could pilot himself. Of course, its travel wouldn't be limited solely to the underground.
"I'll make the size as compact as possible."
The entire body was made of 64 light silver, with the main structural members made of magi-adamantite. The digging blades were also made of magi-adamantite. He had brought the necessary magi-crystals from Uni.
Though things didn't go as smoothly as they would have in the Hourai Island workshop, Jin proceeded with the work efficiently.
"...That's amazing."
"Yes. When Jin-sama gets serious... he truly is the Magi Craft Meister."
Sion and Marikka, who were observing Jin's work, let out sighs of admiration.
"S-So this is Jin-san when he's serious..."
"Incredible..."
Before long, the siblings Lordtoss and Vita had also arrived, watching the work with wide eyes.
"Reiko, pass me that component."
"Yes, Father."
"Hope, hold that part down."
"Yes, Jin-sama."
Jin was so focused on his task that he failed to notice his audience.
That said, since he wasn't in his own workshop, his speed was only at about seventy percent of his usual peak. Nevertheless, the Underground Vehicle was being built at an astounding pace.
＊ ＊ ＊
"Let's do the test tomorrow."
The vehicle reached a functional level of completion that evening. Reiko had stopped him out of concern for Jin, who had been awake since the middle of the night to go to Uni and had spent the rest of the day building the craft.
What he had completed was less of a simple Underground Vehicle and more of a Flying Underground Vehicle—the Rocket Mole. It could handle short-distance flight using a force generator and was also capable of underwater travel. The "short-distance" qualifier was because the interior was cramped and not suited for long-duration boarding.
"If this works, I should be able to liberate Hourai Island."
Jin believed that once that was done, he would be able to consult with Laojun.
Neither Sion nor Reiko said anything. Up to this point, Jin was likely faithfully tracing the actions that his "other timeline" self had performed.
As for the man himself, Jin...
"Jin-san, you were amazing! Just like in Great-grandmother's stories."
"Truly a Magi Craft Meister! I respect you so much!"
...was currently cornered by the siblings Lordtoss and Vita. As they spoke, Jin felt that Vita's appearance and spirit reminded him of both Arshel and Sion.
"Please, tell us all sorts of stories!"
Since they had already finished dinner and bathing and were simply relaxing, Jin didn't mind. However...
"Jin, you're starting early again tomorrow, aren't you? You should rest now. And Vita, don't be unreasonable, okay?"
"G-Great-grandmother!?"
At Sion’s authoritative word, Vita shrank back.
"...Well, I suppose I should."
Jin followed Sion's advice obediently. To be honest, he was feeling quite exhausted. As for Sion herself, she might have just been afraid of Jin exposing the many blunders she had committed in her youth.
That night, a gentle sea breeze blew through the All-Creation clan territory.