Magi Craft Meister

Chapter 690: The Submarine

“Ah, this feels great.”

Soaking in the hot spring, Jin mulled over his thoughts.

“A torpedo powered by the force field generator, slicing through the water and piercing or blowing holes in enemies before returning… But that’s no good. If it falls into enemy hands, it could be analyzed.”

“But, Father, that…”

Reiko quickly interjected with a point. It was the same issue with the golems Jin had created.

“Oh, right. I should program it to self-destruct if it falls into enemy hands.”

“That’s right.”

“Hm, but somehow, I don’t feel right about that.”

Jin felt it was as though he was just using something conveniently and discarding it when it became a problem. The golems, at least, had a level of consciousness and could make decisions, so Jin didn’t feel as guilty about them.

“Maybe the best option is to ensure it can’t be captured by typical enemies.”

Jin’s golems were built to be unbeatable by most opponents—no, even above-average opponents couldn’t defeat them.

“Yes, let’s go with that.”

Having settled his thoughts, Jin left the bath before he got too dizzy.

In the dressing room, Reiko dried his back, as usual. Despite his engagement to Elsa, the relationship hadn’t progressed much. Jin, with his reserved and somewhat old-fashioned nature, wasn’t likely to advance quickly, especially given his upbringing. Back in middle school, his classmates had even called him an “old man,” and he held the belief that there shouldn’t be any premarital relations.

As Jin went out to cool down on the porch, he found someone had beaten him to it—none other than Elsa.

“…Jin, san.”

The way Elsa addressed him still felt distant and awkward, but Jin knew that if he brought it up, it would likely lead to yet another unproductive conversation. So, he silently endured it.

“Are you cooling off too, Elsa?”

“Yeah.”

Penglai Island, located along the Tropic of Cancer, remained relatively warm even in winter.

The two sat together in silence, gazing at the moon in the night sky.

…Or so they thought.

“Father, Elsa, you’ll catch a cold if you stay out here too long.”

Ever-watchful, Reiko, their faithful automaton, spoke up, concerned for their health.

“Shall we head to bed?”

“Mm.”

“Goodnight, Elsa.”

“Goodnight, Jin, san.”

***

The next day, Jin began working on the submarine.

“By the way, Jin… san.”

Elsa, who seemed to have thought of something, spoke up.

“Are the material reserves on Penglai Island being properly managed?”

“Reserves…? Laojun is keeping track of that… I think.”

In other words, Jin wasn’t keeping track himself.

“Hmm, that’s right. I just checked. According to Laojun, in the last year and a half, you’ve used up 20 years’ worth of lightweight silver, 15 years’ worth of iron, and 80 years’ worth of magic crystals.”

Elsa had been taught by her mother, Mine, the previous night, that “a good wife needs to have an understanding of finances.” So, she had taken it upon herself to check the material reserves that morning.

“Ah… Have I used that much?”

“…If this were a normal country, it would’ve faced economic collapse multiple times.”

The unique circumstances of Penglai Island—where mining had continued for a thousand years since the previous master’s era—made it possible for Jin’s consumption to go unnoticed.

“I’m not criticizing you. I know almost all of it was necessary.”

Elsa wasn’t implying that Jin had been wasteful, but it was still something to be mindful of.

“You should at least be conscious of it.”

“You’re right. Thanks.”

“Mm.”

“If I keep consuming resources at this rate, even the underground golems mining on Penglai Island will eventually run out.”

It seemed Jin was reflecting on his actions.

“Alright, after we build the submarine, let’s explore underwater resources.”

Jin now had a clear objective in mind.

“Okay, we’ll base the design on the one we discussed yesterday.”

The submarine’s structure couldn’t be a simple monocoque; it needed reinforced materials to withstand water pressure, with durability, airtightness, and watertightness prioritized.

“Would using adamantite make it too heavy?”

“I think lightweight silver would be better.”

Having spoken her mind earlier, Elsa now joined Jin in constructing the submarine.

“Father, we could also use the exoskeleton of the Gigantopede.”

Reiko suggested. The Gigantopede’s exoskeleton wasn’t as strong as adamantite but was stronger than lightweight silver—and much lighter, too. The downside was that its thin, plate-like form made it unsuitable for use in structural columns or beams.

“Oh, right, we have that. Let’s use it for the outer plating.”

Thus, Jin decided to use it for the submarine’s external shell.

“For the windows, let’s use 10 cm thick… no, triple-layered GS resin.”

This decision was made to increase durability by layering the resin, which was also filled with a flexible magic resin for transparency and self-repair in case of cracks or breaks.

With the materials finalized, construction on the submarine began. Twenty Smith golems and four Daidara golems assisted in the process.

“Jin-nii… Ah!”

Once again, Elsa accidentally called him “Jin-nii.”

“Elsa, I guess ‘Jin-nii’ does sound the most natural to my ears.”

“…Yes, I’m used to calling you that too.”

“…Alright then.”

And so, both decided, without saying much more, to continue using “Jin-nii” for the time being.

“What were you going to say?”

“Oh, right. I recommend keeping a record of the production process.”

This advice came from their experience when they had built a new ship by Lake Wass in the Shouro Empire.

“Ah, I see. Laojun, could you handle that?”

『Yes, Master. However, I believe Reiko would be the best suited for the task.』

Laojun suggested Reiko, showing consideration for her.

“Ah, since she’s closer to the site, that makes sense. Reiko, can I count on you?”

Reiko, of course, would never refuse such a request.

“Yes, leave it to me!”

Reiko, delighted to help, eagerly accepted the task. Her visible joy at being useful to Jin was evident.

“Let’s record it all on a special magic crystal.”

It was faster than writing on parchment and allowed for easy documentation of the engineering magic used. Additionally, with the crystal, Laojun could easily replicate the design.

With Jin, Elsa, Reiko, and Laojun working in harmony, the submarine construction proceeded smoothly.

By the end of the day, the new submarine was completed.

It measured 10 meters in length, about the same size as the ‘Shark,’ with a width of 3 meters, and could carry up to eight people.

Its silhouette was streamlined, more akin to a submersible than a full submarine. While its design wouldn’t look out of place in space, it also wouldn’t seem too unusual if seen floating on the ocean.

The frame was made from 64 lightweight silver, with the outer shell a two-layer composite of Gigantopede exoskeleton and lightweight silver. The interior was coated with a soft magic resin for water resistance and emergency repairs.

Its propulsion systems included both Aqua Thrusters and force field generators.

The armaments consisted of two underwater magic cannons, 10 Aqua Thruster-powered magic bombs, and four guided adamantite torpedoes.

It was equipped with one laser cannon, one sonic cannon that could emit variable frequencies from audible to ultrasonic, and paralyzing guns.

For illumination, it had two powerful searchlights and two auxiliary lights. Additionally, two underwater exploration golem arms were installed for exploration purposes.

For defense, it was equipped with both a magic barrier and a solid barrier, and could also deploy wind and water repelling barriers to reach supersonic speeds if necessary.

For emergency escape, a warp gate was included.

Its energy sources were a magic reactor and a backup ether-based fuel system.

The submarine also included a mana communication device, a magic detection system, and underwater sonar for exploration. An auto-navigation system, using a control core, was also installed.

The biggest challenge for Jin was oxygen supply, but he had a brilliant idea.

“That’s it! We can use engineering magic to extract oxygen from carbon dioxide in the air!”

By extracting oxygen from exhaled carbon dioxide, they could avoid over-oxygenation. For added safety, they installed two systems, ensuring redundancy.

Despite the careful construction, Reiko was tasked with testing the submarine.

“Leave it to me, Father!”

Smiling brightly, Reiko boarded the submarine and spent half a day conducting thorough tests.

As a result, they added a gravity control device. Despite the lightweight materials, the submarine’s weight was just below a buoyant threshold, requiring additional gravity control to help it submerge.

“Ah, I didn’t notice that while building it…”

Though the structure worked out in his favor, Jin couldn’t help but feel a bit down about missing this detail.

“Father, it’s a prototype, so it can’t be helped. Plus, we can make up for it with magic.”

Reiko comforted Jin as she piloted the submarine. Elsa, sitting next to Jin, looked a bit down herself, having been pre-empted by Reiko’s words.

And so, they addressed the issue by adding a compact gravity control magic device.