Compatibility

Using an auto repair shop as cover, along with Carl's Charm Magic, Da Vinci openly turned this place into his own factory. Because of the heavy stench and excessive noise, ordinary dogs would not come near a place like this. Even if they did, the workers would drive them away for being a nuisance.

If Assassin's informants spread throughout the city were dogs, then it would actually be easy to find their blind spots.

After meeting Da Vinci, Carl put the gauntlet over her arm beneath the old man's hopeful gaze. It was a metal structure similar to a bracer, somewhat like a medieval knight's glove. Silver-white, glossy metal blocks rose in layers across it, forming a work of craftsmanship with an intensely industrial beauty. Gorgeous, flickering light flowed through the gaps, making it seem like a futuristic weapon from a science fiction movie.

Carl poured a little mana into it and felt the flowing mana surge through the gauntlet with the force of a hurricane and tsunami. It was as though the gauntlet were alive, spontaneously merging the mana in her body with her own.

"Is this... the fusion of magecraft and science?"

Stunned by the weapon's performance, Carl could not help muttering. Stormy waves churned in her sea-blue eyes along with her mana. As if he had long expected her to ask that, pride appeared on Da Vinci's aged yet vigorous face. His gray brows lifted slightly, and a response came from beneath his thick beard.

"More accurately, this is science."

"This is incredible... Just as expected of Da Vinci."

Carl could not help but sigh in admiration.

If it had merely mixed mana and electricity together, Carl might not have been so surprised. But the speed was simply too outrageous. If someone spent a year building a house, it would be nothing remarkable. But if he built a house in a second, that would be a miracle. Da Vinci had built his own unique production line in a single night and designed a considerable number of weapons...

What terrifying efficiency.

Come to think of it, Carl suddenly recalled that the historical Da Vinci also seemed to value efficiency. His unique Da Vinci sleep schedule allowed him to rest for only a little over two hours a day, dedicating all the remaining time to his research... He truly was someone worthy of admiration.

With admiration for her Servant in her heart, Carl aimed at the only spot in the room not occupied by machinery—the entrance—and threw a punch through the air. Mana raced through her body. The further optimized magecraft formula almost instantly amplified Carl's mana to roughly three times its former level. The flowing mana flooded into her veins, reinforcing her already maximally strengthened body once more. Her strike drove forth a razor-sharp hurricane, and though it had not touched anything, the gale from her fist smashed a dent into the entrance!

The force of the punch alone had such destructive power!

Judging purely by the numbers, that was probably equivalent to B-rank strength!

What a terrifying weapon!

With this... even if I run into Assassin again, it won't be impossible to fight him... As long as I can find a way to make my eyes keep up with his movements next time.

However...

Carl felt the numb sensation returning from her arm. As expected, even with the gauntlet's enhancement, forcefully strengthening her body like that still put a considerable burden on her. It seemed she could only use that full-power state as a trump card.

Yet Carl's earlier praise did not make Da Vinci happy. He kept smiling and began explaining, like an ordinary old man.

In conclusion, what Da Vinci wanted to say was that learning ability was accumulated over time.

No one was born able to grasp the truth of this world. Nor was anyone born with powerful learning ability.

For example, a doctoral student could spend a year studying quantum mechanics and attain a certain level of mastery. But even if a baby spent three years on it, it would be impossible for it to understand quantum mechanics.

Learning ability was an accumulative process. The more a person learned, the stronger their ability to learn itself became.

Da Vinci's ability existed only because he never let anything that could be learned escape him, tirelessly studying everything in this world.

That was why he became a polymath.

That was why he possessed learning ability far beyond that of ordinary people.

That was why the knowledge he had accumulated over his lifetime became his Noble Phantasm, allowing him to join the ranks of Servants.

There was a reason why the saying "master one thing, and you can understand the rest" had been passed down.

Because he knew too many things, no matter what new knowledge he encountered, he could swiftly search the treasure trove of knowledge in his mind for something related or similar. Then he would extract it, establish the connection between the two, grasp the essence of the new knowledge, and finally add it to his knowledge base so that he could continue learning more new things later.

It was like how someone who knew tennis could quickly grasp badminton, or how a chess champion would find learning Go twice as easy.

At Da Vinci's level, he could easily understand magecraft completely unrelated to his own profession.

He could not use magecraft, so he was still a scientist rather than a Magus.

But... he understood the similarities between magecraft and science.

By cleverly understanding the similarities between electrical engineering and magecraft, everything became traceable. If a magic circle was understood as a circuit diagram, then it was merely a matter of one using electricity and the other using mana.

Carl did not quite understand what he was trying to tell her, but she understood that scientists all had their own quirks. Especially regarding terms that ordinary people considered unimportant, scientists were often exceptionally particular.

"With this, even Servants could... Hehe, a Master charging on the front lines? There really have been a lot of such Masters in recent Holy Grail Wars."

Carl was referring to Souichirou Kuzuki from the Fifth Holy Grail War. With Caster's Age of Gods magecraft enhancement, he elevated his refined killing martial arts into a lethal weapon capable of killing Servants... There were also Kirei Kotomine and Kayneth El-Melloi Archibald from the Fourth War. Though neither had any recorded feats of fighting Servants, in conclusion, both possessed combat power capable of contending with Servants.

Da Vinci's ability could also be considered a special form of item creation. Rather than relying on his own magecraft, he used a mechanical factory to genuinely manufacture special Mystic Codes. The advantage was that anyone could use them easily, no matter how far away they were. Moreover, they could be mass-produced.

In that case... the plan can be revised further.

Carl caught sight of the rifle in the corner. It was a rifle modified around the AMX-13, a standard weapon of the modern American military. Its entirely black exterior gleamed with a chilling metallic luster, while some kind of special energy faintly flowed through its body. It was neither mana nor mere electricity... and it was impossible to look away.

According to what Da Vinci had said earlier, this was probably another modified firearm. As the main equipment of the militarily powerful American army, the AMX-13 theoretically possessed an excellent firing rate of 1,400 rounds per minute, an effective range of 800 meters, and a special forty-round magazine. If it could be imbued with power effective against spiritual bodies, it would surely become an overwhelmingly powerful weapon of destruction in this city.

Carl fell into thought over how to make the best use of Da Vinci's item-creation ability. If used properly, Da Vinci would become the finest Servant in this war.

"—Please forgive my presumption. Though I did not receive my Master's permission, I took it upon myself to create something like this."

As Da Vinci spoke, he pressed something on Carl's gauntlet. With a soft click, a knife hilt suddenly sprang out near her arm! Carl curiously pulled it free. It was a small metal knife about the size of a dagger.

Its texture looked utterly ordinary, but the faint glow flowing over it told Carl that it was not nearly as unremarkable as it appeared.

"This is a weapon specially modified for spiritual bodies. I am a Servant myself—a spiritual body—so all I needed to do was analyze myself and reverse-engineer a way for a weapon to gain the ability to harm me. Compared to fists, Master, you prefer firearms and blades, do you not?"

Da Vinci's words made Carl fall silent.

For a time, both figures were swallowed by the insufficient lighting in the room, impossible to see clearly.

After a long while, Carl's voice sounded in the space.

"You... why would you think that?"

"The martial art you use is Muay Thai, correct?"

"Yes. So what?"

"Because you are clearly not someone who practices Muay Thai."

Da Vinci bluntly stated his opinion without the slightest concern for his Master's pride. Carl's face remained hidden in the dim room, her expression impossible to make out.

"Go on. How do I not look like one?"

"Because of the body's structure, Muay Thai leaves large openings around the abdomen. Thus, practitioners must train their abdominal muscles until they are extremely tough, allowing them to withstand attacks directed at their stomachs. Master, while your abdominal muscles are numerous and well-developed, they are not hard. On the contrary, they are extremely flexible. Those are muscles that prioritize agility. They are not meant to absorb damage head-on and protect the internal organs, but to quickly transmit power from the waist to the legs and arms, allowing for more agile and heavier attacks. In other words, muscles that prioritize offense."

"..."

"Second, Master, your elbows do not have many calluses. A Muay Thai fighter's primary weapons are his elbows and knees. The lack of calluses could barely be explained by insufficient training time. However, there are calluses on the web between your thumb and index finger, as well as on the pad of your index finger. Calluses only form through frequent wear. The things that require those two areas are gripping weapons such as swords, or using the index finger to pull a trigger. Neither weapon is something a Muay Thai fighter would use. Furthermore, calluses only form after years, perhaps even more than a decade, of wear. Therefore, I concluded that Muay Thai is merely a martial art you use as a disguise. Your true weapons are blades and firearms."

Da Vinci's words secretly shocked Carl. He had only had one opportunity to observe her body: the moment he drew the magic circle over it. Yet even in that brief time, he had understood her to this extent. It was truly terrifying.

"You've studied not only science, but fighting techniques as well?"

"Not exactly. It is simply that, as a painter, I had no choice but to understand human musculature."

There was neither pride nor fear in Da Vinci's voice.

There did seem to be such a story. In order to understand humanity, Da Vinci had secretly violated taboos and dissected corpses to explore the mysteries of the human body.

"Master, I believe you have your reasons for concealing your combat style. Therefore, I merely provided weapons suited to you."

"Is that so... Then you've truly been a great help."

Carl gave a soft laugh, though its meaning could not be discerned.

"Tell me, Da Vinci, do you know? Without a Holy Relic, the Servant summoned is bound to be the one with the best compatibility with the Master. Do you understand what that means?"

"...Yes. I understand."

"Good. Talking to smart people is always so pleasant."

Leaving those words behind, Carl departed Da Vinci's factory without looking back.

Anyone could tell that having one's secrets exposed was hardly a pleasant experience.

Facing the warehouse, once again empty of all "people," Da Vinci casually smiled. He stroked his gray beard with one hand and sighed softly.

"Because... our compatibility is optimal?"