December 27th.
All preparations were complete. The solution for the Charm-Poison Body was officially implemented.
Personal Space, isolated operating room within the research lab.
Kana, wearing a patient gown, lay on the operating table, her heart uneasy.
'Charm-Poison Body… the problem that had perplexed the Kagero Clan for hundreds of years. Could it really be solved?'
Even though she had witnessed various advanced instruments in this laboratory and understood Ryuji's knowledge and technical comprehension that surpassed the era,
She was still very worried.
After all, this was a problem that the entire Kagero Clan had devoted all their efforts to for centuries without overcoming.
If Ryuji had researched this problem for a few years, over a decade, or even decades, she wouldn't have the slightest doubt. But Ryuji had only researched for one and a half months.
And in such an absurd manner...
Honestly, if it weren't for Ryuji producing various highly effective antibodies during this research process, she would have thought he made up the lie just to groom her into a plaything.
Even now, when he said it was time to implement the solution, she still had no confidence at all.
Perhaps sensing the girl's unease, Ryuji, who was checking preparations on a tool table with his back to her, suddenly asked, "Kana, have you ever thought about a question?"
"Huh?"
The girl was drawn in, looking up.
"This problem, many in your Kagero Clan must have pondered."
"What problem?"
"The harm of the Charm-Poison Body causes the population to decrease over time, but your Kagero Clan persisted for hundreds of years before facing extinction risk. That means your clan's population back then wasn't small, right?"
"It wasn't small." Kana tried to recall, "I remember during family history lessons as a child, the teacher said the Kagero Clan had over five hundred people several hundred years ago."
Finished, she asked curiously, "What's the issue with that?"
"Still no issue?"
Ryuji couldn't help but laugh.
He turned around, looking at the girl with a gaze as if she were a fool, "Since the Charm-Poison Body causes the population to decrease over time, how did you have so many people back then?"
Kana was initially somewhat annoyed by the man's look, but after hearing his later words, her attention was completely diverted.
'That's right!'
'Since the Charm-Poison Body only causes the population to decrease, how did it develop to a scale of hundreds of people several hundred years ago?'
'Could it be that even further back, the Kagero clan had thousands or even tens of thousands of people?'
'No, no, no.'
'No matter how far back in time you go, you can't escape the initial development problem.'
"...I don't know either."
After thinking for a long time, Kana couldn't find an answer. She said, "Our clan experienced turmoil over four hundred years ago. Historical records before that are lost."
"That makes sense."
"What makes sense?"
"My speculation."
"Speculation?"
Ryuji pushed the prepared tool table next to the operating table, continuing, "I have two speculations. First, your ancestors didn't have the Charm-Poison Body; they only acquired this constitution during a certain period, which is why there were so many people before."
Hearing this, Kana couldn't wait to ask, "Can something related to bloodline be suddenly acquired?"
For Kekkei Genkai... by fusing Chakra Natures, one can develop them oneself.
For example, Sunagakure's Magnet Release, Pakura's Scorch Release, and even Iwagakure's Kekkei Tota, Dust Release were developed without relying on bloodline.
But the Charm-Poison Body is a bloodline-based Kekkei Genkai. Although it still operates through Chakra, it cannot be developed solely through Chakra.
Just like the Sharingan and Byakugan.
Both are techniques applying Chakra to the eyes, but without the bloodline, you simply cannot achieve that effect.
"How can't it?"
Ryuji rolled his eyes at her, "Genetic mutation, influence of foreign objects, scientific surgery, and... forbidden techniques related to Yang Release."
At this point, Ryuji fell silent.
He heavily leaned towards the Yang Release forbidden technique answer.
In an unknown distant past, the Kagero Clan had many members, prosperous.
One genius among them utilized or developed a certain Yang Release forbidden technique, creating the Charm-Poison Body, which continued in the descendants' bloodline.
But besides this relatively likely possibility, there was another even more likely one.
"What's the other speculation?"
Hearing Kana's pressing question, Ryuji explained, "The other possibility is that the harm of the Charm-Poison Body is controllable."
"Huh?"
Kana blinked, not quite understanding.
Ryuji had to explain further: "Whether it's controlling the tumor's operation or controlling the poison produced, in short, there must have existed a secret technique to control the Charm-Poison Body, but this technique was later lost."
"You mentioned before that the Kagero Clan experienced turmoil over four hundred years ago... I suspect this might be because some genius developed the Charm-Poison Body, leading to this turmoil, or this turmoil caused the loss of the technique controlling the Charm-Poison Body, resulting in the Kagero Clan's current situation."
"...So that's how it was?"
Kana listened, somewhat dazed.
She didn't know what to feel, only thinking that if so many things hadn't happened back then, the Kagero Clan wouldn't face extinction now, right?
"Kana, your Kagero Clan has devoted centuries to solving this problem but failed consistently. There's a reason for that." Ryuji continued.
Kana snapped back to reality.
She tilted her head, staring at the man, suddenly smiling, "Is it because our clan hasn't produced a genius like you in centuries?"
"Even if one emerged, it would be useless."
The girl's flattery made Ryuji laugh, "Your clan researched the wrong direction from the very beginning, so no matter how talented, it was useless. Not researching how to remove the tumor, nor considering what herbal combinations to suppress the tumor's operation, but to master it."
"...So?"
"I don't know if the power to master it existed in your clan's history, but what I'm going to do now is make you completely master the power of the 'Charm-Poison Body'."
The man's words completely reassured the girl.
She smiled, lying back flat on the operating table, "Then begin, doctor."
"Don't use seduction techniques on me now. It could be fatal."
…
Ryuji didn't know if a secret technique to control the Charm-Poison Body truly existed in the Kagero Clan's history, nor its underlying principles.
So he couldn't create such a set of techniques in a short time.
But he had his own method.
That was the poison sac.
Amegakure's Hanzo achieved super poison resistance and breath with deadly poison by transplanting a black salamander's poison sac into his body.
This gave Ryuji the idea of transplanting a poison sac to control the poison.
Of course, definitely not like Hanzo.
Hanzo himself didn't have the technical skill. After transplanting the poison sac, he still experienced poisoning himself.
And Kana's Charm-Poison was even more potent than the black salamander's poison… it wasn't something so easily accomplished.
He only borrowed this underlying principle to achieve poison control, not blindly imitating Hanzo.
What Ryuji wanted to do wasn't just transplant a poison sac, but to make the sac perfectly integrate with Kana's body, becoming one, like the black salamander.
If it was something originally part of oneself, then there would be no defects.
To put it simply, it was modification and evolution.
Making the Charm-Poison Body advance further, gaining the ability to control poison.
After the war with Amegakure, Ryuji took the salamander corpse.
Through dissection and research of the corpse, he mastered the salamander's body structure, physiological characteristics, and other issues.
He considered using artificial technology to revive the salamander and farm them, to let them become Sunagakure's elite Summoned Beasts...
Cough, getting a bit off track.
Now it's about how to solve the Charm-Poison Body.
Through studying the salamander's body structure and physiological principles, Ryuji mastered how to control deadly poison.
That was to build a separate poison control system.
With the poison sac as the core, construct artificial Chakra Pathways and nerve clusters.
Once the body produces poison, it would be absorbed and stored by the poison sac, ready for use when desired.
Artificial Chakra Pathways and nerve clusters weren't difficult problems. With the knowledge from creating artificial humans, he could create a person identical to Kana down to the last detail, including the soul.
The difficulty lay in the poison sac.
The Charm-Poison was ever-changing, each type possessing extremely potent lethality; even the black salamander's poison sac couldn't withstand it.
If the poison sac was damaged during storage, accumulated multiple poisons erupted, even with poison resistance, there was a very high chance of death.
That's why Ryuji collected as much data as possible on Charm-Poison types.
He used the salamander's poison sac as a base, fused with Kana's poison cells to create a new poison sac, then nurtured it with thousands of Charm-Poisons to improve the sac's capacity.
Thus, a poison sac capable of containing the Charm-Poison's lethality while perfectly matching Kana was created.
This process seemed simple.
But actual operation... just look at the thousands of poisons, think about the countless reactions each poison could have with the sac... anyone with a slight understanding of mathematics knows this was an astronomically large-scale experimental project.
Without the Observation Device's help, relying solely on human computational power, it probably couldn't have been calculated out even in centuries.
Ryuji first anesthetized Kana, then opened her clothes, cut open her abdomen, picked up a scalpel and artificially nurtured pathways to modify the inside.
This was an extremely precise operation. Ryuji worried he might make a mistake, so he had programmed the exoskeleton in advance, letting machines assist in the control.
…
Eight hours later, Ryuji used Medical Ninjutsu (the MC doesn't know it, but it's set on the exoskeleton armor) to heal the girl's abdominal wound, then looked at the body data chart being monitored in real-time by the observation instrument.
'Everything was normal.'
"Hah~"
Ryuji couldn't help but sigh in relief.
He usually created things via 3D Printer, rarely performing modifications personally.
This eight-hour surgery, even with the exoskeleton machinery assisting in control the entire time, left him exhausted.
He pulled down his mask, looking at the still sleeping girl, a faint smile appearing on his face, "Now we'll see how effective the poison sac's control is."