Similar situations were unfolding across various training grounds in the village.
At a secluded training ground near the Hyuga clan's territory, Neji and Lee were engaged in a clash of Gentle Fist versus Steel Fist.
Although Neji ultimately emerged victorious, Lee's ferocious Steel Fist left a deep impression on him, sparking new anticipation for the upcoming final assessment.
At another training ground, Shikamaru, Choji, and Ino were practicing new tactics.
As the new generation of the "Ino-Shika-Cho" trio, their clans' secret techniques naturally complemented each other. They had the frontline-assaulting "Meat Tank," the control-focused "Shadow Imitation Technique," and the unpredictable, hard-to-defend "Mind Body Switch Technique."
Thus, as they gradually mastered their clans' core secret techniques, their team's strength became formidable and not to be underestimated.
Elsewhere, Kiba, Shino, and Hinata were also honing their tactics at a remote training ground.
Their squad boasted the Byakugan, parasitic insects, and ninja hounds with superior olfactory senses, maxing out their reconnaissance capabilities.
As long as they remained cautious, they could evade most powerful enemies.
While all the students at the Shinobi Academy were tirelessly working to improve their skills, Haku and Karin sought out Shinji.
Haku asked, "Shinji, don't we need to practice together at all?"
Karin added, "I heard the other squads are doing last-minute intensive training. Isn't it bad for us to be so idle?"
Shinji waved his hand dismissively. "It's fine. It's just a final assessment, after all!"
Haku cautiously ventured, "Shinji, are you worried that we might hold you back? Please rest assured, we'll definitely give our all in this assessment!"
"Mm-hmm!" Karin nodded repeatedly.
Although Haku and Karin needed to conceal their true strength, they wouldn't let that drag Shinji down. After all, the assessment was conducted in teams of three, and if they hid their abilities too much, it could harm Shinji—a scenario they wanted to avoid.
Shinji patted Haku and Karin on the shoulders. "Don't overthink it! In my eyes, this is just an ordinary assessment."
Seeing that Shinji genuinely didn't seem to care much about the final assessment, Haku and Karin took their leave.
After sending them off, Shinji returned to his desk.
To outsiders, he might have seemed overly relaxed lately. In reality, aside from a brief rest in the first few days after returning to the shinobi world from the Demon Slayer world, he hadn't had a moment's respite.
Even now, the Shinji in the apartment wasn't his real body. His true self was in a secret laboratory not far from the village.
This was also why he declined to train with Haku and Karin.
Haku and Karin were no pushovers now. Training with them using a shadow clone risked exposing his ruse if he wasn't careful. So, he'd rather stay home and keep a low profile than cause any mishaps at this critical juncture.
In Shinji's secret laboratory:
At this moment, inside a newly expanded archive within the underground complex next to the lab, figures bustled about.
It was obvious.
These figures moving to and fro in the archive were all Shinji's shadow clones, created using the "Shadow Clone Technique."
To organize the materials he'd gathered from the Demon Slayer world as quickly as possible, he had to work overtime, essentially doing the work of ten people alone.
Fortunately, his chakra reserves were substantial nowadays. When he ran low, he could use "Wazunagi" to remotely draw chakra from Karin, Yakumo, and others for emergencies. Though mentally exhausted, he could still hold up for now.
While organizing the materials, Shinji gained a deeper understanding of the "Breathing Techniques."
Moreover, by combining his knowledge of medical ninjutsu, he identified several ways to enhance the power of "Breathing Techniques" and further unlock human potential.
Of course.
The human body is incredibly precise yet fragile. Any changes to an established system required extreme caution. Shinji wasn't arrogant enough to believe he surpassed the generations of genius swordsmen from the Demon Slayer world.
His only advantage was the new system of shinobi medical ninjutsu. So, suppressing his impulses, he refrained from rushing to improve the "Breathing Techniques."
Besides deepening his understanding of "Breathing Techniques," Shinji remained relentless in his pursuit of the Rinnegan.
In the laboratory:
After a series of operations at the equipment, Shinji finally obtained the data he sought.
Holding this freshly produced data, he retrieved the records from Karin's physical examination before her initial cell transplant and began comparing them item by item.
"Cell activity is insufficient."
"Chakra fluctuation peaks aren't up to par either."
"Total chakra volume is also an issue!"
The more he compared, the graver his expression became.
Undoubtedly, this new physical examination data was his own. Comparing it to Karin's data before her initial cell transplant, he found his metrics were noticeably inferior to hers.
But this was expected.
After all, Karin was a member of the Uzumaki clan, naturally excelling in chakra volume, cell activity, and vitality compared to him.
Shinji's advantage lay in his possession of the Eternal Mangekyo Sharingan, with its Yin Release chakra quality far surpassing Karin's at the time of her initial cell transplant.
"This is my only edge. I must leverage it to maximize my success rate," Shinji mused.
Transplanting the First Hokage's cells was a hurdle for anyone. Even for the current Shinji, whether he could clear it was uncertain.
If he underwent the surgery himself, he might not be able to activate "Wazunagi" in time to transfer excess Yang Release chakra out of his body.
When Yakumo and Karin underwent the procedure, they had both slipped into varying degrees of unconsciousness. If Shinji couldn't endure and fell into a coma during the surgery, he might never wake up. Thus, no amount of caution was too much for him.
Setting down the physical examination report, Shinji approached another piece of equipment to check his chakra strength.
After obtaining the results, he compared them to the records on the equipment's logbook and thought, "My Yin Release chakra has improved again today. It seems my Eternal Mangekyo Sharingan hasn't reached its peak yet and can still be nurtured by the 'All Creation Power.'"
After some deliberation, Shinji made up his mind.
He decided to wait until his Eternal Mangekyo Sharingan reached its absolute limit, fully nurtured by the "All Creation Power," before undergoing the First Hokage's cell transplant surgery.
This approach would cost him some time but was safer and more reliable.
According to his estimates, as long as he could successfully endure the First Hokage's cell transplant, the path to achieving the Rinnegan would be smooth sailing.