Shinichi's study of medical ninjutsu progressed rapidly.
With his knowledge of Keiketsu (Nerve acupuncture points) from his past life and Tenketsu from this one, mastering human anatomy and chakra physiology came naturally. Two systems, nervous and chakra pathways, ran almost parallel, never merging except at the eight critical points in the body.
Two in the brain. Five along the spine. One in the heart.
These channels didn't just connect chakra and nerves, they also linked the circulatory system, forming gateways between physical energy, spiritual energy, and chakra.
After the discovery, Shinichi opened one of the spinal channels.
And immediately–
"UWAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA!!!!!!!!!"
He collapsed, sealing the channel as pain tore through every fiber of his being.
His muscles spasmed. His organs screamed. His bones felt hollow. And his nerves rang like sirens.
He had triggered a forced conversion of physical and spiritual energy into chakra, exceeding his natural capacity.
But the result wasn't chakra.
It was something else.
'This… it's closer to Ki. But not quite. It's unstable. Wild. And incomplete.'
Shinichi lay on the grass, gasping for breath, his body trembling.
Slowly, he gathered chakra and spread medical ninjutsu through his body to accelerate recovery.
'Perhaps… I should've started with the brain. These channels are much smaller. The side effects could've been less risky….'
Shinichi closed his eyes and inspected his body once more. The brain, spinal cords and the heart.
Heart was the core of chakra generation.
The major conversion point of physical energy into chakra.
'Opening all of these channels… would be suicide. Close to Instant death. It would explosively drain physical energy, then spiritual energy.'
It was clear that unless the body is trained to an extreme there was no meaning to using them.
But a deeper question lingered.
'Why do these channels exist? It's almost like chakra was introduced into the body – artificially. These channels were created to convert physical and spiritual energy into chakra.'
Shinichi noticed something else.
'Physical energy drained faster than spiritual energy. Only a small portion converted into chakra... once it reached maximum chakra capacity, the rest… became pseudo-Ki, an explosive and unstable energy.'
As Shinichi analyzed his experience, he recalled the ancient technique:
Hachimon, the eight gates, used by desperate shinobi as a final, suicidal attack. But most died instantly, unable to control the explosive burst of power, unable to make significant difference in actual combat.
'People were aware of these channels since ancient times. But they never refined them, or they found it too risky to refine them.'
As his body recovered and his mind became clearer, Shinichi continued with his analysis.
'The energy conversion was mutual. Some chakra converted back into physical and spiritual energy. Can the rates be controlled? Can one channel favor reverse conversion?'
He considered testing other channels. Then stopped himself.
'No. I don't lack chakra. I don't need this technique.'
Shinichi's chakra volume was immense.
His body's Yin and Yang chakra organs continued to expand his reserves. Moreover, Shinichi regularly trained his stamina and meditated. At this point, his chakra rivaled adult elite shinobi.
His chakra control and elemental manipulation were already superior to the average Uchiha clan shinobi.
If he fought seriously, he could match, or even surpass, some of the elites.
Moreover, he hadn't trained or developed offensive jutsu, yet.
He was preoccupied with understanding Uchiha physiology; with finding a way to safely stimulate or activate the chakra organs; on breaking the so-called curse of hatred.
That's why, despite his interest in Tobirama's Hiraishin, he shelved it.
His Sharingan had already scanned the seal in full detail and had a rough understanding of the theory. But, it simply wasn't his current priority.
---
Shinichi left a shadow clone at the Academy, while his main body ventured into the woods
He hunted wild animals; captured them, injured them, healed them, killed them and revived them.
He tested the limits of medical ninjutsu.
How long could a body remain dead and still be revived?
The answer varied by size. But he found a baseline.
Seven minutes. The minimum window for revival using standard medical ninjutsu.
Two hours. The minimum window for revival if the heart was controlled and the blood circulation maintained via chakra.
After two hours, even if the subjects were 'revived' and basic physiological functions were restored using the medical ninjutsu, they remained still, as if they were soulless. Their physical aspect was restored, but the spiritual aspect was lost.
But these were the conclusions based on his test on animals. Not humans.
***
Time passed.
Shinichi had mastered most of the medical ninjutsu content granted to him.
Now, he turned his attention to the Mythical Palm Technique.
He was genuinely surprised.
'Tobirama gave me this? Such an advanced technique…'
He had assumed Tobirama's reward would be limited to basic healing methods.
But this–
'Perhaps I misunderstood the Nidaime… He truly is trying to move forward. Trying to shed the narrow clannism of the Warring States Era.'
Shinichi understood the implications.
Giving this technique to him was akin to giving it to the Uchiha clan.
And yet, Tobirama had done it.
'His sincerity is real. Even if his subconscious still views us – Uchiha – as a threat… he's trying.'
Shinichi respected that.
The Mystical Palm Technique required: 1. Master-level chakra control. 2. Proficient Yang chakra manipulation. 3. Extensive anatomical knowledge.
Such advanced medical ninjutsu was rare and scarce.
In other clans, medical ninjutsu was crude and underdeveloped.
Although Tobirama wouldn't consider it refined. Only the Senju, with natural affinity for Yang chakra, had refined the medical ninjutsu into a true discipline.
Shinichi knew that this technique could be traded for advanced ninjutsu or secret arts with other clans. Its value was immense.
Senju medical ninjutsu was divided into two core parts:
Chakra Harmonization: The healer converts their chakra into a neutral form that can be accepted by the patient's chakra system. This avoids rejection and allows the chakra to restore physical and spiritual energy and accelerates the patient's natural healing process. Mystical Palm Technique: An advanced form using Yang chakra instead of neutral chakra. it requires finer control, but uses less chakra overall. The user can selectively target areas, passing chakra through cells and tissues and instantly replenish depleted physical energy and mend injuries at a visible rate with surgical precision.
Shinichi studied both. He mastered the first already and Mystical Plam Technique was not far behind.
He began to understand the deeper mechanics of Yang chakra.