In some works of fiction, Science and Technology gave more "common" individuals the ability to face threats of an incomprehensible nature.
It is common in North American comic books for impossible machines to bend the laws of reality in ways that are only permitted to superior entities.
In other works, it is common for the supernatural to be combated with the technologically advanced, as is the case in that Universe plunged into a War for the mastery of the Galaxy.
Ancestral entities that mortals can only conceive of as Gods, challenged and studied by brilliant minds whose only limitations are usually time and resources.
The World of Naruto was no exception.
Filled with mysticism and a power system based on the fantastic, the impossible, and the supernatural, the Shinobi World was not exempt from these brilliant minds.
Take the extinct Land of the Sky. A non-canonical element, yet interesting for the advancement of its methods.
Genuine machinery, operating under mechanical and mystical principles in a unique harmony.
Take the researcher and creator of the Chimera Forbidden Technique, Hiruko of Konohagakure.
A geneticist like no other, capable of doing what the Villages, in their barbarism, could only have achieved by kidnapping shinobi who carried Kekkei Genkai and forcing them to produce offspring.
Take Orochimaru, the greatest exponent of Science and the Mystical who is part of the Canon. His feats regarding the study of Chakra and its many mysteries are unrivaled in the Ninja World.
He would have achieved so much more had he possessed higher quality equipment.
And while Tetsumaru and Mei did not possess the genius of that enigmatic character, they did have much more advanced technology and support in their pursuit of power.
—But this is unnecessary, Tetsumaru!— Mei complained through their bond while her body was being studied by a select group of researchers.
Nezu and Tetsumaru watched from the side, with the Director sitting on a floating Satetsu platform while executing several commands on his tablet.
—It's for the sake of science, Mei— Tetsumaru replied, filtering some of the sensations he felt while looking at the kunoichi in her underwear, strapped to a cold metal table with sensors covering her skin and connected to countless wires.
A massive screen in the center projected a hologram of Mei's body. Beside it, a digital image displayed the schematic of the Tenketsu points that Ragdoll had provided to the shinobi.
The sensors were analyzing Mei's energy signature, specifically the Yang aspect of her chakra.
Tetsumaru figured that, since it originated in the cells, that part of the chakra should be measurable. He wasn't entirely wrong.
Nezu had already developed a method to preserve pure chakra in containers. He had studied it in detail, finding himself more fascinated by the Yin aspect than anything else; even with all the equipment at his disposal, he couldn't quantify that other half of the chakra.
But the Yang half was enough.
—You may begin now— Nezu called out suddenly. Tetsumaru nodded and relayed the message to Mei, who remained inside a glass chamber to ensure the sensors weren't interfered with by external agents.
The kunoichi proceeded to slowly mobilize the energy in her body, accumulating it in large quantities and keeping it just below the stress point of her Tenketsu.
The sensors worked, searching for any anomaly present in the Nervous System, which served as the medium through which the chakra pathways dispersed that energy throughout the body.
—Thermal increase in the esophageal section— one of the researchers alerted, eyes glued to the screen where a rain of data descended rapidly.
Nezu received the data and analyzed it. Tetsumaru tried to take a look, but he didn't understand a damn thing and resigned himself to trusting the rat/bear/dog.
To him, things were much simpler.
—Initiate Bio-Quantum Resonance Tomography— the Director ordered. Tetsumaru rolled his eyes at the cliché terms but remained silent, communicating with Mei instead.
Speed up production throughout your entire body.
—If any of these perverts looks at me for more than a second, tear their eyes out— she retorted, uncomfortable with the exposure of so much skin before the many adult men in the room.
The chakra ignited, and Mei gritted her teeth, forcing it to flow intensely throughout the entire length and breadth of her body.
It was different from flooding her arms and back to strike, or her legs and spine to move at high speeds. Only a few individuals cover their entire body with chakra in such a manner.
Little by little, the empty diagram representing Mei's body in real-time began to fill with small points and tiny channels that resembled the aforementioned nervous system.
Having found the correct frequency and knowing exactly what to look for, the sensors were reprogrammed; with Mei's effort, they were able to track every abnormal heat signature in her body.
In two minutes, the entire path the chakra used to circulate through the kunoichi's body was successfully mapped.
After a period of analysis and death stares from Mei, it was Tetsumaru's turn to enter the room and be mapped.
This was the first phase of their next training plan.
To ensure he didn't explode or suffer a heart attack, Tetsumaru took it upon himself to explain in greater detail the process by which they executed their techniques, as well as the inherent dangers of the experimentation.
With the information provided, Nezu used his powerful mind to find a solution. What they were doing now was putting that idea to the test.
First, they would map the so-called chakra pathways, and Nezu would develop a program to run reliable simulations on the effects of energy movement, wavelengths, intensity, the resistance of the points, and so on.
With this program at their disposal, Tetsumaru and Mei would proceed to mold chakra using hand seals in different patterns, triggering the specific movements in the specific zones that each seal activates.
In this way, according to the Director, the program would run the simulations and search for the safest patterns, discarding everything that produced strain on their Tenketsu or directly caused the pathways or nearby organs to burst.
It wasn't perfect, and there was information that Nezu lacked: the influence of the Yin aspect in the entire process.
As a more esoteric energy, Nezu was unable to detect it, and neither Tetsumaru nor Mei possessed enough skill to manipulate both halves separately. Nor did they dare to try.
So they had to act with caution regardless. However, this signified a massive breakthrough in the development of Ninjutsu.
And something Nezu wasn't aware of was that the pair's status as incarnations gave them a certain instinct—or perhaps muscle memory—when it came to weaving seals to unleash a technique.
In Tetsumaru's case, almost all of the Third Kazekage's techniques were unknown to him, as there was no way Sasori had mastered Magnet Release and Iron Sand in the same way the man himself had.
Mei had it a bit easier in this regard, as the woman she embodied had more screen/page time, and she wasn't the only user of Water, Vapor, and Lava in history.
Orochimaru may have had a unique mind. Hiruko may have persevered in his field. The shinobi of the Land of the Sky may have possessed mechanical knowledge far ahead of their time.
But Tetsumaru and Mei had the power of a modern society backing them, as well as the support of one of the most intelligent creatures in the world—if not the most.
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A/N: For anyone wondering:
I know Mei Terumi's Yōton isn't exactly magma like Roshi's. In the official translations, it's often referred to as "Dissolving Element". Even though they share the name Yōton, the kanji used for Roshi's lava is actually different.
That said, I chose to use Lava for the cinematic effect rather than that ugly green goo. Since Mina already uses acid, I didn't want to repeat the same power.