Satoru didn't hide too much, as he had other trump cards anyway:
"Yes, I haven't mastered very strong Lightning Release techniques yet. Due to my age and physical limits, I don't have much chakra."
"Your Lightning Release seems to consume physical endurance instead of chakra, right?" the Third clarified.
"Yes, teacher," Satoru nodded.
"In that case, I already know how to train you. First recover your strength, then we'll work on your endurance training. Once your endurance grows, very few people in the shinobi world will be able to beat you.
"As your endurance increases, so will your chakra. That way, using ninjutsu or your special Lightning Release, you can either quickly defeat opponents or wear down those stronger than you.
"Remember your strengths, think about your weaknesses, develop your strong sides and compensate for the weak ones—that way, you'll always win.
"Rest well. As soon as you're rested, come to me right away," Sarutobi affectionately ruffled Satoru's hair and left with fatherly warmth.
The village leader ordered the ANBU to secretly guard Satoru, allowing him to recover peacefully in the hospital.
As soon as he recovered, the boy immediately went to his mentor. The Third thoroughly analyzed their recent fight, and Satoru realized his shortcomings and learned much.
Only then did he truly understand the greatness of Tobirama's protege.
Hiruzen Sarutobi wasn't some brute warrior swinging a staff mindlessly. He was a man who loved studying ninjutsu and analyzing others' fights as post-lunch entertainment. This meant many of his techniques were the result of accumulated knowledge and training. Initially, the head of Konoha preferred fighting with ninjutsu and taijutsu, and his stance toward other villages was quite hardline.
But now, in middle age, the Third seemed to have rethought much. Raw power alone wasn't enough anymore, so his policies had become much softer. That was what dissatisfied Danzo.
"Satoru, actually, relations between villages are like relations between people. If there's harmony and potential for better mutual development, there's no need for military conflicts."
Hiruzen not only taught the transmigrator combat but also often shared some ideas about village management. This deeply touched the boy and let him see his teacher's true nature.
The Hokage combined firmness and flexibility. Initially, his policies were quite hardline, then he balanced strength and adaptability, and in old age, he preferred avoiding unnecessary trouble—all for stability and peace in Konoha.
He was also a man who valued old ties. This was evident in how he let Orochimaru go—he greatly cherished people with exceptional talents.
The transmigrator didn't disappoint his mentor. He answered some of his questions very skillfully, earning the Third's deep fondness.
Once those conversations ended, Satoru's physical endurance training officially began.
Hiruzen's endurance training was, essentially, very simple—running.
At first, the boy was surprised. While running could build endurance, the effect wasn't that obvious. But when he learned he'd have to run with weights, he understood his teacher's intent.
"Summoning Technique!" the Third Hokage immediately summoned Monkey King Enma. Enma had an indestructible body, and though very agile, his weight was unimaginable.
Imagine making a four-year-old child run around the training ground with Enma on his back. Such a task was simply impossible for an ordinary person.
Satoru possessed Tsunade's Monstrous Strength, but that power usually manifested explosively during attacks, not in everyday life.
Now, the boy had no choice but to use Monstrous Strength for endurance training.
Carrying Enma on his back with Monstrous Strength was fairly easy at first. But by the second lap, Satoru found his strength nearly depleted, and running turned to walking.
Yet, despite that, he gritted his teeth and persisted. Since endurance was his weak point, he naturally had to work diligently to improve it.
Every time the system slave wanted to give up, he remembered his goal.
He had to become Hokage and change the entire shinobi world!
No matter the hardships, he endured in the end.
And the Third Hokage, seeing Satoru's diligence each time, felt mixed emotions.
"Such a genius, working on himself so selflessly. I think there's no one more diligent than him in the entire shinobi world," the village leader's fondness for Satoru grew day by day.
Of course, if the day consisted only of endurance training, Satoru would be relatively free. But in reality, he had to do missions every day too. For a ninja, completing tasks is part of the job. C-rank and D-rank missions—Satoru had to keep doing them constantly.
So Satoru's training continued for half a year. Finally, one day Sarutobi told him:
"You've already completed plenty of C- and D-rank missions. From today, you'll fight me for two hours every day!"
Hiruzen Sarutobi, as an absolute Kage-level expert, had incredibly rich combat experience. His skills in ninjutsu and taijutsu were unmatched. He was ready to be Satoru's whetstone, and the boy was naturally overjoyed.
Each time fighting the Third, the Earth native enriched his combat experience. After each defeat, he analyzed the reasons.
Of course, Satoru wasn't incapable of beating his mentor. He just temporarily refrained from using his Devil Fruit abilities for future growth.
Some more time passed.
"Lately, you've been fighting me constantly, and your progress is becoming more obvious. Now I'll teach you ninjutsu."
Satoru had been waiting for these words like manna from heaven. For the "Professor of Ninjutsu," techniques were naturally his strongest suit.
The Third deciding to teach the orphan ninjutsu meant he had fully acknowledged the boy as his important personal student. The previous fights were just to develop strengths and compensate weaknesses; now it was time to learn new techniques.
"Our Sarutobi clan secret technique, Great Flame Technique. Do as I do," Hiruzen ordered very seriously.
The head of Konoha formed the seals once, and Satoru already memorized them firmly. After all, he had super perception, could see others' chakra, and even had a one-tomoe Sharingan. So Satoru instantly grasped the essence of the Great Flame Technique.
On his first try, he unleashed incredibly scorching flames capable of incinerating an opponent, vividly demonstrating its power.
"The Sarutobi clan's Fire Release seems no inferior to the Uchiha clan's techniques," the boy marveled.
But Hiruzen Sarutobi himself was the most surprised. He hadn't expected Satoru to master the Sarutobi clan's most complex Fire Release technique so quickly.
"Satoru, I once said you have astonishing talent. It seems I still underestimated you."
***
Read the story months ahead of the public release — early chapters are available on my Patreon: Granulan