Not far from where Rin stood on the blood-drenched battlefield, a group of shinobi emerged—clad in muted grey armor, no hitai-ate on their foreheads. Konoha's Root ANBU.
"Check the bodies. Confirm the number of dead Uchiha. Make sure no one's alive," barked their captain, his voice cold as steel.
"If you find even one breathing Uchiha—execute them on the spot."
"This is the first time Root has moved directly against the Uchiha. No one must leave this place alive. Nothing can be allowed to leak and jeopardize the Foundation's future plans."
The Root captain issued orders without hesitation.
The village had begun moving in the shadows, using any means necessary to dismantle the Uchiha's military strength.
Even losing the war against Sunagakure would be preferable to letting the Uchiha eclipse the Hokage's faction.
That much was agreed upon by nearly all of Konoha's leadership.
The captain wasn't acting on personal will—he was following orders.
"Yes, Captain!"
His subordinates immediately fanned out, sweeping the area for survivors.
Moments later, one of them returned, visibly unsettled.
"Captain, the bodies are too jumbled to get an exact count… the carnage is beyond anything we've seen. There are Iwa corpses mixed in, too. We can't determine an accurate number."
"But judging by the scale of the remains, at least a hundred shinobi are dead—most of them Uchiha."
"No survivors so far."
"Also… the Sharingan. They're all missing."
"They might've been taken by Iwa-nin."
Even these hardened Root operatives, trained to feel nothing, felt the weight of the scene. The scale of slaughter chilled them.
But the missing Sharingan—that disturbed the captain most.
"Leave two here to incinerate the corpses and clean the site. The rest, with me—we're hunting the Iwa-nin. Recover the Sharingan at all costs."
The mission had changed.
Their orders were clear: the Sharingan must not fall into enemy hands.
None of them suspected that any Uchiha had escaped.
After all, Iwa's ambush was supposed to be flawless.
But once they found and interrogated the remaining Iwa-nin, they learned the truth—every single attacker had died on the field.
The Sharingan hadn't been taken by Iwa.
They had been taken… by an Uchiha.
The Root captain immediately relayed this information back to the village.
To suppress the growing hawk faction within the Uchiha and erase the lingering echoes of Uchiha Setsuna's rebellion, Konoha's leadership had elevated the village-loyal pacifist, Uchiha Fugaku.
He now stood as head of the Police Force and clan leader, supported by many who believed peace could be negotiated.
A lapdog of the Third Hokage.
At this time, the Third was still in his prime.
A Kage-level shinobi who mastered all five chakra natures.
His talent may have even surpassed the Second Hokage.
The Uchiha had no means of confronting such a monster.
If Rin returned to the village now, he'd likely be used as a political offering—sacrificed to soothe tensions.
He needed power before going back.
Power to protect himself.
Once Shisui's fever stabilized and the boy was no longer in immediate danger, Rin stopped treating him.
He turned instead to the new power he had acquired—
[Evolution Calculus]
A power that allowed him to calculate the path of genetic evolution.
Each evolution yielded mysterious rewards.
Rin speculated that for the Uchiha, evolution meant the progression of the Sharingan, the refinement of their bloodline.
Through exhaustive trial and error over an entire day, he managed to isolate fragments of his own Otsutsuki DNA—and confirmed his theory.
The path forward was clear: awaken the Sharingan, then evolve it.
The Uchiha bloodline was, at its root, an incomplete strand of Otsutsuki heritage—infused with dormant elements of the Tree's genetics.
The act of awakening the Sharingan allowed these latent genes to express themselves.
Only by identifying both strands—the Otsutsuki core and the Tree trait—could he map out the route for future evolution.
By splicing and integrating foreign genetic elements, he could refine this blood further.
Normally, the Otsutsuki and Tree fragments couldn't activate together.
But if expressed simultaneously, they would produce unique organelles within ocular cells—organelles that completely rewired the eye's structure, birthing the Sharingan.
The energy created by these structures fused with the user's mental power, producing a specialized chakra nature.
The Sharingan itself was a manifestation of yin chakra, unique to the Uchiha.
Rin theorized this phenomenon to be a genetic mutation triggered by the fusion of Otsutsuki and Tree traits—
After all, pureblood Otsutsuki didn't possess the Sharingan.
There had to be a lock suppressing the gene's expression.
And every lock could be opened—with the right key.
That key… was emotion.
Everyone knew Uchiha awakened their eyes through intense emotional trauma.
And Rin, a former doctor, knew exactly what that meant on a biological level.
It was all chemical.
Adrenaline—the hormone released in response to emotional stress.
He isolated it through simulation.
Just one run of Evolution Calculus, and he had not only awakened the Sharingan…
He had also pinpointed the trigger: surges in adrenaline.
The higher the hormone concentration, the more likely the ocular mutation would activate.
From his past life, Rin recalled multiple methods to boost adrenaline.
The easiest: drugs.
Either through direct injection—
Or self-harm, which stimulated pain receptors and caused a hormonal spike.
But here, on a battlefield?
Self-mutilation was too risky.
That left one method: chemical stimulation.
Rin chose to synthesize the compound.
The earliest adrenaline-stimulating drug had been derived from ephedra.
Its active ingredient: ephedrine—an alkaloid compound.
And in this forest, ephedra had to be growing somewhere.
While watching over Shisui, Rin scoured the woods.
Two days passed.
Shisui gradually recovered.
His strength returned, and his Sharingan awakened during the ordeal—his power growing rapidly.
"Rin, are you looking for something? I can help," Shisui offered, his voice tentative but genuine.
He'd observed Rin's behavior and drawn his own conclusions.
He was sharp.
He knew Rin was searching for something.
"No need. I found it," Rin said calmly, raising the ephedra plant in his hand.
It was rare. He'd scouted nearly ten kilometers along riverbanks before finding a patch on a small plain.
Extracting ephedrine in a lab was easy.
In the wild, it was a nightmare.
But Rin was a ninja.
He had fire release jutsu—perfect for makeshift heating.
He built a rudimentary distillation rig, using simple heat to separate the alkaloids.
The result: a crude extract—rich in toxic ephedrine.
Lethal in the wrong hands.
But for a trained medical-nin like Rin, suppressing the side effects wasn't an issue.
Without hesitation, he downed the liquid.
Almost immediately, he felt it.
Excitement surged through him.
His nerves sparked like electric wires, consciousness sharpening.
Then came the pain.
A tingling, burning sting crawled beneath his skin.
His eyes flew open involuntarily.
Red veins spiderwebbed across his sclera, bursting like capillaries.
The white of his eyes was devoured by crimson.
And in the center—
Where his dark pupil once rested—
A single tomoe rotated into existence.