Project GB is an official initiative by Re:Library.

After entering the atelier, the first thing Melua and I did was spread out the specification sheet I had prepared for my engineering department project.

Before doing anything else, we needed to review Marie’s requested customizations while checking the specifications.

Of the two requests, extending the range of the magic cannon was comparatively straightforward. We simply needed to make the barrel longer. It was a rather brute-force solution, but by simple calculation, doubling the barrel length would likely achieve roughly double the range.

The real problem was the other request: she wanted something that could hit its target faster than a bullet without using bullets.

“But even setting the range aside, what’s actually faster than a bullet?”

Peering at the specifications, Melua asked the question with obvious curiosity.

As she pointed out, there were very few things that could travel faster than a projectile propelled by an explosion.

“It’s not impossible. The fastest thing would be light.”
“Yeah, but only people with a Stigma can use light magic, right?”

I nodded at Melua’s accurate observation. She had clearly considered the possibility herself.

A Stigma was a birthmark bestowed upon those said to have received the blessings of the Three Holy Flower Goddesses. Like a Pure Eye, it was an innate trait one was born with and was regarded as proof of divine favor.

And, as Melua said, only those bearing a Stigma could use light magic.

“Right. This is one thing that can’t be compensated for with simplified formulas. So the idea of using light itself is off the table.”

The problem that had stumped even a Special-Class Alchemist like Melua for an entire year hadn’t been easy for me either.

The next possibility I considered after light was wind.

Inspired by Estea’s Tempest, I explored the potential of wind magic. However, the kinetic energy generated by wind pressure was too small to launch a projectile effectively. And even if we abandoned physical ammunition and tried firing wind magic alone, air resistance would likely cause the spell to disperse before reaching its target.

So I rejected that idea as well.

But while thinking about Estea, another idea surfaced—one inspired by Hom’s Blitzraid.

If I applied the principle behind that technique—the way lightning magic was projected along the rails and converged on its destination—I might be able to launch lightning magic itself like a bullet.

“…But what about lightning?”

After showing Melua the simplified formula I had written on the back of the blueprint, I spread out the main design and asked for her opinion.

“Huh? That’s it?”

Melua’s deflated reaction was understandable.

The blueprint I had drawn was extremely simple: a long rectangular barrel made from four plates, with a grip and trigger attached to the rear.

“That’s right. Decorations can always be added later. The important part is this—the heart of the magic cannon.”

As I explained, I pointed to the reverse side of the blueprint.

There, I had drawn the simplified formulas that would be engraved onto the four plates forming the barrel.

“We engrave Spark Shot formulas into the four plates that make up the barrel.”
“On these!? I mean, if it’s you, Master, I’m sure you can do it. But will it actually fire? Four Spark Shot formulas at once sounds like it’d generate a ridiculous amount of heat.”

I had already accounted for that.

Glancing around the shelves of Melua’s atelier, I located the section where the materials I wanted were stored.

“It’s not like I haven’t thought about that. I want to use Ithildin and Dumanium.”

Ithildin was one of the highest-grade alchemical metals, commonly used in the armor plating of Mecha Soldiers, while Dumanium was an alchemical material most often used in things like the tires of steam-powered vehicles.

“I get wanting something tough and durable, so I understand choosing Ithildin. But why Dumanium?”

I knew Melua was asking from an informed perspective. Dumanium was also used in the tubes that formed a Mecha Soldier’s magic-contraction muscles because of its exceptional elasticity and pressure resistance.

So, while preparing the alchemical furnace, I elaborated a little.

“I want to make use of a different property altogether. It’ll be easier to show you than explain it. Mind if I walk you through it while we’re transmuting?”
“Of course!”

Melua answered immediately and fetched the Ithildin and Dumanium from their respective shelves.

The Ithildin, an extremely valuable metal, was stored inside a wooden box and further wrapped in anti-corrosion paper. One glance was enough to tell it was a high-quality material, already refined into ingots.

The Dumanium, which was vulnerable to degradation from sunlight, had been formed into palm-sized spheres and stored in a light-shielded wooden box wrapped in cloth.

As expected of an atelier prepared specifically for Melua, both the selection of materials and the way they were managed were absolutely impeccable.

“Everything’s in excellent condition. Next, let’s use a mana liquefaction catalyst as a solvent and create transmutation fluids from the Ithildin and Dumanium.”
“We’re making them already?”
“Of course. We don’t have much time, so we should make progress whenever we can. I want to assemble the barrel tomorrow, so could you prepare the alchemical furnace?”

Melua nodded and began setting up the furnace.

“Because we’ll want to pour it into the mold while it’s still hot, right?”
“Exactly. While we’re melting the materials in the alchemical furnace and producing the transmutation fluids, we’ll also need to make a clay mold out of Kaitaba.”

There was still some Kaitaba left over from when we repaired Hom’s guitar yesterday, so we could simply reuse that.

“By the way, Master? What was that other property you wanted to use?”

While preparing the furnace, Melua raised her voice to ask.

Ah, right. I had said I’d explain it during the transmutation process.

“Dumanium is also an insulator. If we make use of that property, we can prevent the barrel from becoming excessively charged and overheating, and it eliminates the risk of the user being electrocuted by the magic cannon.”
“Hm? I think I get the idea, but wouldn’t that interfere with Spark Shot? The material you’re engraving the simplified formulas into would itself be an insulator, right?”

Melua tilted her head and pressed for clarification.

“That’s right. Which is why the trick lies in the formulas themselves. We engrave the simplified formulas into a composite material made from Ithildin and Dumanium, both of which are insulating. Then we fill those engraved channels with a conductive liquid metal, creating a path for the shot to travel. If we extend the formula pattern all the way to the muzzle, the Spark Shot will run along the engraved characters of the formula itself.”
“Oooh! So simplified formulas can be used like that, too.”

At last understanding the structure of the magic cannon, Melua let out a sound of admiration.

Even while we talked, she skillfully continued the transmutation of the Ithildin and Dumanium.

　　　＊　＊　＊

Before long, the Ithildin and Dumanium transmutation fluids were ready, so we poured them into the four long plate molds we had made from Kaitaba.

“Once these cool and harden, we’ll engrave the simplified formulas.”
“I could cool them down with ice magic. Want me to?”
“No, let’s not this time. We’ll let them cool naturally.”

Dumanium aside, Ithildin was a metal that hadn’t existed in Glass’s era. I didn’t want to do anything reckless and risk degrading the properties of the transmuted material.

“Then I guess that’s it for today~. Ahh, it’s just that you’re so efficient, Master. Everything feels like it’s over in the blink of an eye.”
“Really? I think you’re just as efficient, Melua.”

I wasn’t being modest—I genuinely meant it as praise for her work. But Melua blinked in surprise.

“No way~! I’m not even in the same league! I mean, Estea told me all about it. Apparently you’re amazing at cooking too, right?”
“…She told you about that?”

I was a little surprised to hear my cooking brought up by Melua. Then again, she and Estea were roommates, so it wasn’t exactly strange for them to talk about such things.

“Told me? More like I heard you spent the New Year holidays together, and I was insanely jealous!”

Melua spoke excitedly, but then suddenly seemed to realize something and closed her mouth.

“…Ah, but part of the reason was that Estea couldn’t go home for the holidays, so I never actually told her I was jealous to her face… probably…”
“I’m sure Estea understands that concern of yours.”
“Right? You think so too?”

Given that Estea knew Melua even better than I did, that was especially true. When I reassured her, Melua let out a relieved sigh.

“Whew… I wanted to try your cooking too, Master~. …Oh! Come to think of it, didn’t we forget to buy ingredients for the sweets!?”
“Well, if it’s just sweets, I can always bring some over to the atelier.”
“Yay! I seriously love how quickly you make decisions, Master!”

Melua’s friendly, open smile was so infectious that I found myself smiling in return.

Ever since she had practically forced me into becoming her master and established our mentor-disciple relationship, I had started to lose track of which of us was supposed to be the older one.

Perhaps, despite being recognized everywhere as a genius alchemist and granted authority and independence at such a young age, Melua had felt a certain loneliness somewhere along the way.

It was probably different from the loneliness I had experienced in my previous life.