Inside the laboratory.
Senju Tobirama had no idea that his recent actions had been witnessed by Senju Hashirama and Uchiha Madara.
Tobirama skillfully placed Renya on the experiment table, then restrained his limbs to prevent muscle reflexes during the procedure.
After finishing everything, Senju Tobirama looked with satisfaction at the unconscious Renya, then took out the [Uchiha Observation Manual] from his robes.
On the opened page, it read—
[The Rebellious Shadow Clone?]
Ever since Renya had learned the Shadow Clone Technique, there had always been something wrong with the clones he created.
In combat it didn't matter, but in daily life, the problems were severe.
Sometimes, they would go so far as to dismiss themselves on their own.
Most importantly, Renya's shadow clones were extremely disrespectful toward him!
Without the slightest respect!
Even more evil than those wicked Uchiha themselves!
Senju Tobirama once asked Renya about it, but the boy said he didn't know—his very first shadow clone had behaved this way.
Even as a well-versed master of forbidden techniques, this was the first time Tobirama had encountered such a situation.
He had been too busy with other research to deal with the shadow clone problem.
Now, he had specifically dragged Renya here to get to the bottom of it.
Senju Tobirama leaned close to observe Renya, recording notes on the notebook with swift strokes.
"This brat's physical fitness keeps getting stronger."
"It seems my original hypothesis was right—his bodily functions have indeed improved drastically."
"I wonder if, in the end, he can catch up to Brother?"
When he had discovered the secret between the Senju and Uchiha clans, Tobirama had suspected that merging their bloodlines might cause some kind of transformation.
So he secretly began a series of experiments, studying both his own blood samples and Renya's.
And indeed, he found that the fusion of the two bloodlines—
Could make the body's cells more active and far stronger than before.
The rate of cell division accelerated, enhancing physical recovery and mental strength, with chakra reserves abnormally vast—
Far beyond that of ordinary Senju or Uchiha.
After long-term observation showed no immediate danger, he secretly began injecting small amounts of his own blood cells into Renya's body.
That was the true reason behind Renya's dramatic physical changes over the years...
As the experiment continued, Tobirama was shocked to discover that Renya's cells had been steadily multiplying year by year!
Perhaps in only a few years,
Renya would reach the same level as his elder brother.
Even more shocking—
The divided cells could go on to create new cells, continuing the cycle endlessly!
One cell division creating another…
This meant Renya's rate of aging would be drastically slower than normal.
According to Tobirama's estimates, Renya's lifespan could reach between one hundred and one hundred and twenty years.
And since his cells continued to grow, it was uncertain how long he might ultimately live.
Upon realizing the transformation in Renya's body, Tobirama knew he had personally created a monster.
His first thought back then had been to kill Renya.
If this boy were allowed to keep growing, he might well become another Uchiha Madara!
The Uchiha were prone to extremism in their thinking—if one day Renya chose a dark path, there would be no one in the shinobi world able to stop him.
Reason told Tobirama to strangle the danger in its cradle.
But looking at the unconscious boy, he had been unable to do it.
By then, he had already spent years with Renya, and in his heart, had acknowledged this Uchiha brat.
Naturally, he could not bring himself to kill him.
In the end, it had been his own doing, and this boy was innocent...
Senju Tobirama resolved to guide the child properly, never allowing him to go astray.
And should Renya one day walk the path of extremity, Tobirama would personally end the life of this adopted son.
Fortunately, in these ten years of living together, Renya had never once caused him worry.
The boy not only loved the village, but also cherished his comrades, cooked excellent meals, and had achieved great contributions on the battlefield.
He had already become the perfect successor to the Hokage.
Tobirama was deeply thankful that he hadn't killed Renya back then.
This boy really was different from the other Uchiha.
His thoughts drifted back to the present. Looking at the unconscious Renya, Tobirama's lips curved slightly upward.
"You really haven't disappointed me, brat."
He continued writing down the unfinished data.
Through observation, he deduced that the problem came from Renya's mental energy, causing the shadow clones to develop rebellious thoughts.
Such a case was extremely rare. Tobirama wondered—had Renya's spirit always been flawed? Or was it a side effect of the experiments?
There was no clear solution yet. He would have to wait until morning to ask the boy directly.
Perhaps then they could resolve the issue.
Seeing that there was still time, and that the anesthetic's effect lingered, Tobirama prepared to continue monitoring cell division.
He opened Renya's shirt, exposing the well-defined muscle lines, and drew a small sample of blood from his chest with a syringe.
The moment he removed the needle, the puncture healed instantly.
Tobirama dressed him again, then carried the syringe over to the experiment table.
...
At the edge of the Senju clan's forest, Senju Hashirama and Uchiha Madara hid behind a tree.
"Where exactly did Tobirama take that boy?" Madara was growing impatient. "Why haven't they come back yet?"
They had been waiting for hours, and dawn was already approaching, yet there was still no sign of their return.
Madara, already harboring resentment toward Tobirama, now felt even more suspicious.
That man must be up to something shady.
"Madara, don't worry." Hashirama wore his usual hearty smile, trying to ease the tension. "Tobirama should be back soon."
"Renya is his adopted son—he would never harm him…"
Before he could finish, Madara cut him off coldly.
"Of course you trust him. But don't forget, he is Senju Tobirama—the man who has always distrusted the Uchiha to his very bones."
Though Madara claimed not to care about clan matters, he couldn't accept Tobirama's behavior.
After all, he had once been heavily guarded against by Tobirama himself.
That feeling was intolerable.
"Madara, calm down. That won't happen."
Hashirama hurried to reassure his friend, worried he might lose patience and leave the village.
He had worked so hard to bring Madara here, and hadn't even gotten to taste Renya's cooking yet—how could he let him leave now?
If Madara was going to leave, at least wait until after breakfast!
He had been craving that food for two years.
Madara gave a cold snort and closed his eyes, as if to rest.
Just then, faint footsteps sounded in the distance.
They saw Senju Tobirama walking slowly toward the Senju compound, carrying the unconscious Renya on his back.
He was completely unaware of the two figures hidden in the trees.