As the First Hokage's cells were implanted, the expected intense rejection reaction kicked in!
On the operating table, Mumei curled up in pain, struggling to suppress herself, letting out only soft whimpers.
Shinji monitored the chakra state in Mumei's body using 'Jikibi' while observing the instruments surrounding them.
From the data, though the rejection reaction was strong, it hadn't crossed the critical threshold, so there was no immediate worry of the First Hokage's cells going out of control in Mumei's body.
Shifting his gaze from the instruments, Shinji asked Mumei, "How do you feel?"
"Shinji, it hurts so much!"
Mumei's response came with difficulty.
"Hold on. I went through this pain too. It's a necessary part of fusing with the First Hokage's cells. As long as you endure it, everything will be fine!"
Shinji encouraged her.
At this point, there wasn't much more he could do. He had already thoroughly explained and emphasized everything she needed to know. Now, it was up to Mumei herself!
As the first, most intense wave of rejection began to subside, Mumei's expression softened slightly.
Following Shinji's advice, she gritted her teeth and recklessly mobilized her Yin Release chakra to fuse with the Yang Release chakra contained in the First Hokage's cells.
In an instant, the Yin-Yang fusion began!
Shinji's expression sharpened as he thought, "Looks like she's already leveraging the strength of her Yin Release chakra."
From the few successful cases of First Hokage cell implantation, aside from Yamato's stroke of luck, others—whether Obito, Danzo, Yakumo, Karin, or Shinji—relied on their Yin Release chakra to balance the Yang Release chakra in the First Hokage's cells.
In this regard, Mumei's advantage was undeniable!
Time ticked by.
In the blink of an eye, an hour passed.
Mumei, still curled up on the operating table, gradually relaxed her body, the pained expression on her face fading.
Shinji let out a sigh of relief.
Though the fusion process wasn't entirely smooth, Mumei had managed to endure it with her formidable Yin Release chakra.
At this stage, the transplant surgery could essentially be declared a success. The only uncertainty was how long it would take Mumei to fully subdue the implanted First Hokage cells.
Even so, Shinji didn't dare let his guard down, staying by the operating table, constantly monitoring Mumei's vital signs.
Two more hours passed, and Mumei, her forehead drenched in sweat, fully woke from her daze.
With a whoosh, she sat up, looked at her hands, and murmured softly, "What a strange feeling!"
Shinji smiled, "Congratulations!"
Mumei turned to Shinji, "I succeeded?"
Shinji nodded lightly, "Yes, the surgery was a success. You should be able to feel the changes in your body now, right?"
Mumei focused inward and said, "I feel a stream of chakra running wild in my body, but as long as I draw it with my Yin Release chakra, it comes rushing over. That must be the Yin-Yang fusion you mentioned! Overall, I feel my chakra has increased, and the change is still ongoing!"
"That's the 'All Creation Power' born from the union of Yin and Yang," Shinji explained. "It not only boosts your chakra reserves but also enhances your dojutsu and comprehensively transforms your body." After a pause, he continued, "If you can fully complete the fusion and absorb the Yang Release chakra in the First Hokage's cells, the lingering effects of being sealed for a century should be completely eradicated!"
Mumei said confidently, "That's not hard at all!"
Shinji smiled, "For you, indeed it isn't."
For most people, absorbing the Yang Release chakra in the First Hokage's cells required gradual effort, using nature transformation to slowly make it their own.
Shinji and Yakumo had done so.
As for Karin, her Uzumaki clan Sage Body and exceptionally high-quality Yang Release chakra, with innate healing properties, made absorbing the First Hokage's cells easier for her, an exception.
Mumei was different. With her 'Yachihoko,' her chakra control was nearly unmatched in the current shinobi world, surpassing even Shinji with his 'Jikibi' and 'Wazunagi.' In this situation, as long as she was willing, fully consuming the Yang Release chakra in the First Hokage's cells was no challenge.
After Mumei went to the adjacent training ground to adapt to her post-surgery body, Shinji sat at his desk.
Mumei had unsurprisingly passed both the Eternal Mangekyo Sharingan fusion and the First Hokage cell transplant surgery with flying colors.
Once she adapted, her strength would undoubtedly skyrocket, soon approaching or even surpassing Shinji's own level during his Eternal Mangekyo Sharingan phase.
In this scenario, Shinji's backup 'Infinite Tsukuyomi' plan was now feasible.
Opening his notebook, Shinji began scribbling and sketching.
According to his calculations, after fully adapting to the Eternal Mangekyo Sharingan and completely absorbing the First Hokage's cells, Mumei's dojutsu power should more than double.
In other words, the number of targets her 'Yachihoko' could mark would also increase exponentially.
If Mumei's 'Yachihoko' could ultimately mark ten thousand targets, Shinji's 'Infinite Tsukuyomi' plan could begin preparations.
The chakra in the shinobi world was primarily divided among shinobi, tailed beasts, and various summoning beasts, including those from the three sacred grounds.
Shinji couldn't accurately judge the proportion of chakra each held, but shinobi undoubtedly accounted for the lion's share. Otherwise, Black Zetsu wouldn't have gone to the trouble of tampering with the Uchiha's forbidden stone tablet, tirelessly manipulating Uchiha Madara to launch the true 'Infinite Tsukuyomi.'
Only by reuniting all the scattered chakra in the shinobi world could Kaguya Otsutsuki, sealed by the Sage of the Six Paths and his brother, be revived.
Estimating the number of shinobi in the world wasn't difficult.
In the original timeline's Fourth Great Shinobi War, nearly the entire shinobi world was involved, with almost all shinobi villages, including the samurai of the Land of Iron, participating.
The Shinobi Alliance numbered around eighty thousand. Including shinobi from smaller villages not involved in the war, rogue shinobi, wandering shinobi, and others, the total number of shinobi in the world was likely around one hundred thousand.
So, if Mumei's 'Yachihoko' could mark ten thousand targets, it would cover at least one-tenth of the shinobi world's shinobi—an astonishing number.
If the marked targets were selectively chosen, such as focusing only on villages like Hidden Leaf with stronger overall shinobi, the effect could be doubled!