Compatibility

Using the auto repair shop as a cover, along with Karl's Charm Sorcery, Da Vinci had brazenly turned the place into his own factory. The strong stench and loud noises meant that ordinary dogs wouldn't come around. Even if they did, the staff would drive them away for getting in the way.

If the assassin's eyes and ears spread throughout the city were dogs, then it would be easier to find blind spots.

After meeting with Da Vinci, Karl slipped on the gauntlet under the old man's hopeful gaze. It was a metal structure resembling an arm guard, similar to a medieval knight's vambrace. Piles of silver-white, lustrous metal blocks bulged on it, forming a piece of craftsmanship with a highly engineered aesthetic. Beautiful, shimmering light flowed through the seams, like a futuristic weapon from a sci-fi movie.

Karl injected a little magical energy into it and felt the flowing magic transform into a power comparable to hurricanes and tsunamis as it passed through the gauntlet. It was as if the gauntlet had a life of its own, spontaneously merging his body's magical energy with Karl's.

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

Karl, astonished by the weapon's performance, couldn't help but murmur. His sea-blue eyes churned with the magical energy like a stormy sea. As if he had predicted Karl's question, Da Vinci's aged but energetic face broke into a proud smile. The old man's gray eyebrows twitched slightly, and a response emerged from beneath his large beard:

"To be precise, this is science."

"It's amazing... just as expected of Da Vinci."

Karl couldn't help but sigh in admiration.

If it were just a mixture of magic and electricity, Karl might not have been so surprised. But the speed was incredible. It was like one person building a house in a year, which was nothing special. But if he built a house in one second, that would be a miracle. Da Vinci had set up his own unique production line and designed quite a few weapons in just one night...

The efficiency was astonishing.

Thinking of this, Karl suddenly remembered that the historical Da Vinci also seemed to value efficiency. With his unique Da Vinci sleep method, he only rested for a little over two hours a day, dedicating the rest of his time to his research... a truly admirable person.

With respect for his Servant, Karl aimed at the only spot in the room not occupied by machinery – the doorway – and threw a punch. Magical energy surged, and a more optimized magic circuit instantly amplified Karl's magic to about three times its usual power. The flowing magic poured into Karl's veins, further strengthening his already maximized body. The punch, accompanied by a sharp hurricane, created an indentation in the doorway with sheer force, despite no contact!

Just the wind from his fist had such destructive power!

If judged purely by data, this was probably equivalent to B-rank Strength!

(What a terrifying weapon!)

(With this, I might even stand a chance against an ASSASSIN next time... as long as I can figure out how to keep up with his movements.)

However...

Karl felt a tingling sensation in his arm. As expected, even with the gauntlet's enhancement, reinforcing his body so recklessly still placed a considerable burden on him. It seemed this all-out effort could only be used as a trump card.

Yet, Karl's previous praise didn't please Da Vinci. He maintained his smile and explained to Karl like a normal old man.

In conclusion, Da Vinci wanted to say that [learning ability] is accumulated.

No one is born with the ability to grasp the truths of this world. No one is born with a powerful learning ability.

For example, a doctoral student might spend a year researching quantum mechanics to a certain level of understanding. But an infant, even after three years, could not possibly comprehend quantum mechanics.

Learning ability is a process of accumulation. The more a person learns, the stronger their [learning ability] becomes.

Da Vinci's ability was simply because he never let go of any opportunity to learn, continuously and tirelessly studying everything in this world.

That's why he became a polymath.

That's why he possessed a learning ability far beyond that of ordinary people.

That's why the knowledge he accumulated throughout his life became his Noble Phantasm, allowing him to ascend to the rank of a Servant.

The saying "learning from one thing, understanding many" has been passed down for a reason.

Because he knew so many things, he could quickly search his mental treasure trove of knowledge for anything related or similar to any new piece of information, then refine them, establish their relationship, and understand the [essence] of the new knowledge, finally adding it to his knowledge base for future learning.

It's like if someone knows how to play tennis, they can quickly master badminton. If someone is a chess champion, learning Go will be twice as effective with half the effort.

At Da Vinci's level, he could easily understand [magic], which was completely unrelated to his primary field.

He didn't know magic, which is why he remained a scientist, not a Magus.

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

He cleverly understood the similarities between electrical engineering and magic. If magic circles were understood as circuit diagrams, then everything would become traceable. The only difference was that one used electricity, and the other used magical energy.

Karl didn't quite understand what Da Vinci was trying to tell him, but he knew that scientists had their quirks, especially when it came to terms that most ordinary people found insignificant.

"With this, even a Servant... Heh, a Master charging on the front lines? The recent Holy Grail Wars have been quite active, haven't they? Such Masters."

Karl was referring to Souichirou Kuzuki of the Fifth Holy Grail War, who, with the enhancement of Caster's Age of Gods magic, elevated his exquisite killing fist techniques into a fatal weapon against Servants. There were also Kirei Kotomine and Kayneth El-Melloi Archibald from the Fourth War. Although they didn't have the record of fighting Servants, in conclusion, both of them possessed combat power comparable to Servants.

Da Vinci's ability could be considered a special form of [Item Creation]. Not through his own magic, but through a mechanical factory, he could genuinely create special [Mystic Codes]. The advantage of this was that anyone could easily use them, regardless of their location. Moreover, they could be mass-produced.

(In that case... the plan can still be modified.)

Karl glanced at the rifle in the corner. It was a rifle modified around the AMX-13, a standard firearm of the modern US military. Its all-black exterior gleamed with a chilling metallic luster, and a strange energy flowed faintly along its body. It didn't seem like magical energy, nor was it simply electricity... it was captivating.

According to Da Vinci's previous explanation, this was likely a modified firearm. The AMX-13, as a main battle equipment of the US military with its superior military strength, theoretically had an excellent rate of fire of 1400 rounds per minute, an effective range of 800 meters, and a 40-round magazine. If it could be imbued with power that affected spiritual bodies, it would undoubtedly evolve into an absolutely formidable weapon in this city.

Karl fell into thought about how to best utilize Da Vinci's item creation abilities. If used properly, Da Vinci would become the most outstanding Servant in this war.

"—Please forgive my presumption. I created this without the Master's permission."

Da Vinci said this and pressed a button on Karl's gauntlet. With a soft click, a handle suddenly sprang up near Karl's arm! Karl curiously pulled it out. It was a small metal knife, about the size of a dagger.

Its texture looked ordinary, but the faint glow flowing on it told Karl that it was not as unremarkable as it appeared.

"This is a weapon specially modified for spiritual bodies. I myself am a Servant (spiritual body), so by analyzing myself, I can deduce how to make a weapon capable of harming me. Rather than fists, wouldn't the Master prefer firearms and swords?"

Da Vinci's words left Karl speechless.

For a moment, both of their figures were obscured in the insufficient light of the room, making them difficult to see clearly.

After a long pause, Karl's voice echoed through the space.

"You... why do you think that."

"The martial art you use is Muay Thai, isn't it?"

"Yes, and so what?"

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

Da Vinci stated his point with sharp accuracy, disregarding the Master's feelings entirely. Karl's face was hidden in the dimly lit room, making his expression unreadable.

"Continue? What makes you say that?"

"Due to the physical structure of Muay Thai, the abdomen is left very exposed. Therefore, practitioners must train their abdominal muscles to be exceptionally tough to withstand attacks aimed at the stomach. While your abdominal muscles are numerous and well-developed, they are not hard. On the contrary, they are very soft. These are muscles that prioritize flexibility, not for withstanding frontal damage to protect the organs, but for rapidly transferring power from the waist to the leg and arm muscles, enabling more agile and heavier attacks. In other words, they are muscles that emphasize offensive capability."

"..."

"Secondly, your elbows do not show significant calluses. The primary weapons of a Muay Thai practitioner are their elbows and knees. The lack of calluses could barely be explained by insufficient training time. However, you have calluses on the webbing of your hand and the pads of your index finger. Calluses only form from frequent abrasion. The two things that utilize these areas are gripping weapons like swords, and pulling a trigger with the index finger. Neither of these weapons is something a Muay Thai practitioner would typically use. Furthermore, the formation of calluses is bound to take years, even decades, of wear. Therefore, I deduce that Muay Thai is merely a martial art you use as a disguise, and your true weapons are swords and firearms."

Da Vinci's words secretly startled Karl. He had only seen his own body once, when he was inscribing the magic circle on it. Yet, even in that brief moment, Da Vinci had managed to understand him to this extent. It was truly terrifying.

"Not only science, but you've also delved into martial arts?"

"Not at all. It's just that, as a painter, one must understand human muscles."

Da Vinci's voice carried neither pride nor fear.

It seemed there was indeed such a tale, that Da Vinci, in his pursuit of understanding humanity, had not hesitated to secretly transgress taboos and dissect the dead to explore the mysteries of the human body.

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

"Is that so... That's a great help, then."

Karl let out a light chuckle, the meaning behind it impossible to discern.

"Say, Da Vinci, do you know? Without a Catalyst, the Servant summoned is inevitably the Servant with the greatest compatibility with their Master. Do you understand what that means?"

"...Mm. I understand."

"That's good. It's always a pleasure to converse with intelligent people."

With that parting remark, Karl left Da Vinci's workshop without looking back.

It was easy to imagine that having one's secrets exposed was hardly a pleasant experience.

Facing the now empty warehouse, Da Vinci smiled casually, stroking his white beard with one hand, and mused softly.

"Because... we have the greatest compatibility?"