A Promise to Meet Again

 

「By the way, Prometheus. I’d like to consult with you. I know recreating WDM would be difficult, but… could something similar be achieved with current Silhouettes? Could you at least tell me what’s feasible? Or maybe give me a hint?」

Kou shifted the subject. He didn’t want to waste this rare chance to speak with Prometheus. He wanted a weapon capable of recreating phenomena close to the WDM.

「Gladly. Astraea, would you lend a hand?」

「Understood.」

「WDM is impossible with current Silhouettes. Especially with Unit 5, which uses armored muscles. But… something similar might be possible. Let’s start by discussing what defines a solid. It’s when temperature drops, particle motion slows, and inter-particle binding forces cause them to arrange in a dense, orderly fashion. That’s the general idea of freezing. We often use Kelvin and Celsius to measure temperature.」

「Right. Even the kind of cold we use in metalworking gets called ‘cold.’」

The name Cold Blade, from Gogyou Heavy Industries, followed the same convention—referring to cold working. Though Kelvin was the scientific standard, Celsius was more commonly used. With water’s melting point at 0°C and boiling at 100°C, it remained a familiar metric.

「Now, there are various phenomena where plasma crystallizes into a solid. Duct plasma crystals, for example, are observed at -272.15°C. They’re known as Wigner crystals or Coulomb crystals. Even in your time, Kou, people were theorizing spacecraft without mechanical structures using Coulomb crystals of duct plasma.」

「Because those crystals can only form in a vacuum, they’re applicable to spacecraft.」

「Exactly. Building components out of plasma has that science fiction flair, right? Coulomb crystals are heavily influenced by gravity, so they’re limited to space. But that’s not what you’re after. What you need, Kou, is the technology to compress plasma into a solid. Am I right?」

「High-pressure physics!」

「Correct. The principle behind metallic hydrogen. Take oxygen, for example. At 6 GPa, it solidifies; at 100 GPa, it becomes metallic. That’s because the crystal structure changes and the electron configuration of the molecules shifts. Did you know solid oxygen becomes vividly colored? That phenomenon is called molecular dissociation. It was predicted and proposed by a scientist named Wigner—and later proven. Technology using this theory should help improve Astraea, Arges, and the others.」

「‘We can’t use theories that don’t exist on Earth’—the main rule controlling the technology seal, right?」

「Wigner predicted that any insulator could become metallic under enough pressure. Metallic hydrogen is the prime example. Even if we can’t produce WDM outright, there are plenty of applications. Now, by using high-frequency waves and high-output lasers—」

Prometheus launched into a lecture. It was enough to capture the full attention of Astraea, as well as Abel and Morgan.

◆　　◆　　◆　　◆

「Incredible… Even with current tech, this much is possible?」

「As expected of the super AI who laid the foundation for the Silhouette system.」

Kou couldn’t help but admire what he’d heard.

Meanwhile, the AIs exchanged information at high speeds, optimizing and sharing new techniques.

「Unit 5 probably won’t benefit much, though. Sorry.」

「It’s more than enough. If my allies grow stronger, Unit 5 will be able to fight even harder.」

Prometheus had proposed a series of new armaments.

Indeed, Unit 5 might not gain much directly, but even Prometheus expressed admiration for the D-rifle. The fact that such firepower had been achieved without relying on optical weaponry or electron-excited explosives was truly astonishing.

Kou made a mental note to share this with Aki and Nyanta later.

「Our engineering tech has also received an update. Or rather, it’s now better optimized for the current technology. It should be of great help to you, Kou.」

「That’s right, Arges. With this, we’ll be able to create even better things.」

Arges and Steropes continued to process information in real time.

They were now refining the synergy between Pioneering Era and Interplanetary War Era tools and tech, and the technology currently liberated, adjusting it to allow for increasingly complex operations.

「—Time’s about up. This was fun, Kou! Everyone!」

From WDM to Kou’s current technological limits and their potential extensions, Prometheus had been enthusiastic in sharing it all. Arima and Polymetis had supported his computations.

While Kou and Prometheus spoke, the AIs were concurrently exchanging and refining data at high speed.

Astraea and Eirene bowed deeply. Even the Hora-class AIs had received an unexpected version upgrade from this.

「Time already…? That flew by.」

「I’m only here on probation, after all. I wish I were sealed like Arima—with just half of my body sealed away. Polymetis’ processing power and Arima, who’s still sealed in Tartarus, worked together to create a setting where I could emerge more easily.」

「You are under a really nasty seal. You must’ve really pissed off Hermes.」

「I did provoke him plenty.」

「Wish I could’ve seen it. That was before I was born, after all.」

Even Prometheus seemed to recognize he may have gone too far.

「Kou. Asia’s Aimer. Everyone… until we meet again.」

「We will meet again, Prometheus. That’s a promise.」

A promise to meet again—an incredibly important one.

Prometheus felt the same. A promise carried deep, heartfelt meaning.

「I’m honored! Yes, we’ll definitely meet again!」

With that joyful smile, Prometheus vanished, as if stepping out for a stroll.

Kou remained still for a while, quietly gazing at the place Prometheus had stood.

◆　　◆　　◆　　◆　　◆

Unit 5 sat atop Bastet’s back along the shoreline. Asia’s Aimer stood behind Kou.

「Looks like it’s about time.」

「You don’t get to ride on the back of a Mythology Weapon every day.」

Kinukawa was practically vibrating with excitement.

Behind them rode the Aramasa atop Hayatarou, with the Akors turned into a backpack—now a permanent trio.

Kinukawa had even forced himself into the back seat of the Aramasa’s MCS, declaring he wouldn’t miss this for anything.

With them were Libya still inhabiting Arthur’s body, Flack aboard her, and Aki and Nyanta aboard Epona.

「If anything happens to this group, the entire Nemesis System might collapse.」

Asia laughed. The gathering was truly that extravagant.

「You’ve got us protecting you.」

A Nereid replied. She and the other Nereids were piloting the Nixies—Triton-class Quattro Silhouettes modified for deep-sea conditions—that had been produced in Realm.

Unit 5 and the other Lanius were suited with adapted equipment originally meant for gas-giant exploration. They could function even 10,000 meters below sea level—but at the cost of nearly all mobility.

「This might be our final voyage—our last great adventure in Planet Libya.」

Asia looked up at Kou and smiled brightly.

She looked genuinely excited. And no doubt, Aimer felt the same.

「Adventures are the best.」

「Totally. Imagine—this is a place not even the creator of the planet knows about!」

「It won’t be without danger.」

「Not to worry. The Guardian of the Sea is with us.」

A massive catfish poked his head above the surface, swiveling his neck as he scanned the Trireme’s squad.

Spotting them, he swam over happily.

Bahamut hauled himself ashore, dragging his huge body like a sea serpent.

「Wait, catfish can go on land?」

「Many species do. They have lungs. Clara—the walking catfish—is a famous one.」

Libya, their resident ecosystem expert, answered Kou’s question.

「Clara walks upright? …Never mind. I think the Biwa Lake Giant Catfish also comes ashore to spawn.」

No one was sure what mental image had just flashed through Kinukawa’s mind.

「The hatch opened… So we’re really riding a catfish, huh.」

「It’ll be fine.」

Asia chuckled, speaking to Kou. After all, it wasn’t every day you got to ride a giant catfish to the bottom of the sea.

「We’re counting on you, Bahamut.」

「Nya!」

Kou and Bastet spoke as they boarded through the open hatch.

The other Silhouettes followed. The hangar was of a familiar design standard.

「Yep. The inside is the same as any other spaceship.」

「So normal it’s suspicious…」

Someone approached them on quiet footsteps.

It was Bahamut’s avatar.

He looked up at the towering Silhouettes and bowed politely, walking with his twin tail fins acting as legs.

「Let’s head down to the hangar.」

「Yeah.」

Asia’s suggestion was met with a nod from Kou, who stepped nervously out of the cockpit.

Bahamut waddled over. Kou held out a hand, and Bahamut looked up in surprise—then eagerly gripped it with his gill-fins. Kou used both hands to shake in return.

Asia followed suit.

「Gyuu! Gyuuu!」

Bahamut squealed in delight.

「Nyaa~」

Asia responded in fluent cat language.

「He says, ‘Welcome, most humbly!’」

「Thanks, Bahamut.」

Bahamut gave another polite bow. Kou couldn’t help but think—what a humble sea dragon god.

The pilots of the other Trireme’s crafts also disembarked to greet Bahamut. Nyanta was already chatting with him in cat language.

「So catfish can make sounds. First I’ve heard of it.」

Kou mumbled in curiosity.

「They don’t have vocal cords, so they rub their pectoral fins together to make sounds.」

「Biology is wild…」

Bastet, the cat Eidolon, watched it all with satisfaction.

「Bahamut’s a good one.」

「It pains me that I remain trapped inside this Silhouette.」

Libya watched the interactions with envy.

「Hang in there, Libya-neechan. You’ll be out soon.」

Flack offered words of comfort.

「You’re a fine young man. No wonder Arthur chose you as his contractor.」

Flack rubbed his nose, bashful.

「The ship’s functions are all intact. Has it really been maintained this whole time?」

「Hoping one day people would board him again?」

「Yes, nya. Bahamut’s been waiting for this day—for many humans to come aboard. His dream has been fulfilled, nya.」

「And there’ll be many more passengers to come.」

Kou was certain of it. Right now it was just the Trireme’s crew, but soon, many more from Planet Libya would join them aboard Bahamut.