The more he mulled it over, the more excited Uchiha Shinji became.
As the core figure in his 'Rinnegan Plan,' Karin's strength was the key to whether the 'Rinnegan Plan' would succeed.
And to increase the plan's success rate, both Karin's Yang Release chakra and Yin Release chakra had to reach their absolute peak!
On the Yin Release chakra front…
As long as Karin could restore her fully depleted Mangekyo Sharingan this time, Shinji was at least thirty percent confident he could help her fuse them into an Eternal Mangekyo Sharingan.
Though it wasn't the ultimate peak, it at least met the threshold to pursue the Rinnegan.
As for the Yang Release chakra front…
As a member of the Uzumaki Clan, with a healing physique exceptionally rare even among her kin, Karin's Yang Release chakra was already formidable.
Add to that the White Zetsu cell transplant Shinji had previously performed on her, which had further elevated the quality of her Yang Release chakra.
At this point, it was essentially at its limit.
If he wanted to push Karin's Yang Release chakra even further, the only path left was to directly transplant the First's cells.
After all, White Zetsu cells were a product of Uchiha Madara diluting the First's cells with the power of the Divine Tree.
In simpler terms, White Zetsu cells were a watered-down version of the First's cells.
They traded reduced potency for a higher transplant success rate and lower difficulty to control.
Without Tsunade's surgery for Yakumo this time, Shinji wouldn't have dared to attempt transplanting the First's cells into Karin so easily.
But if Tsunade succeeded this time, he could copy her method, replicating the surgery on Karin and boosting the 'Rinnegan Plan' success rate once more.
"This step was absolutely the right move!"
He secretly rejoiced.
Having Yakumo agree to become Tsunade's disciple was originally just a desperate measure to preserve the Koryugan and gain a channel to the village's higher-ups.
He hadn't expected Tsunade to deliver so many pleasant surprises.
Setting aside everything else, just the surgical plan Tsunade had crafted for Yakumo held far too many lessons worth learning.
And so, through 'Jikibi,' he said to Yakumo, "I've reviewed it. This surgical plan is extremely thorough. You can wait for the surgery with peace of mind."
After a moment's hesitation, Yakumo replied, "My lord, are you really letting Lady Tsunade perform this surgery on me?"
Undoubtedly.
Compared to Tsunade, Yakumo trusted the leader who had changed her life far more.
"No need to worry. I'll be watching over you from the shadows!"
Shinji naturally wouldn't tell Yakumo that even he was eagerly awaiting this chance to study Tsunade's surgical techniques.
And he wasn't lying either.
When Tsunade performed the surgery on Yakumo, he would activate 'Jikibi' and 'Wazunagi' to monitor Yakumo's physical condition.
If anything went wrong during the surgery and the Yang Release chakra in the First's cells started to rampage, he would use 'Wazunagi' to extract as much of the runaway Yang Release chakra as possible, buying Yakumo a slim chance at survival.
Soon, the news that Tsunade would perform a First's cell transplant surgery on Yakumo caused a massive stir within a small circle.
The strongest reaction, without a doubt, came from the Kurama Clan.
The consequences of transplanting the First's cells were something a prominent clan like the Kurama Clan understood all too well. Back in the day, during the large-scale experiment supported by the village to recruit volunteers and recreate Wood Release for Hidden Leaf, a Kurama clansman had even signed up.
But the result? Dozens, maybe hundreds of volunteers, and not a single survivor.
The thought of the eldest daughter of the main family, tasked with reviving the clan, facing such a brutal surgery made the Kurama Clan reject it from the bottom of their hearts.
But after learning that Yakumo's body could no longer bear the strain and the surgery couldn't be delayed, Yakumo's father overruled all objections, agreeing to the surgery on behalf of the Kurama Clan.
When the Third Hokage learned of Tsunade's decision, he pondered for a long time before asking, "Is this the only way?"
"Hm!"
Tsunade nodded, sparing no extra words.
The Third then posed another question, "If something goes wrong during the surgery, can you ensure the Koryugan is preserved?"
Tsunade froze.
"If an accident happens, those eyes will be Kurama Yakumo's legacy—and a precious legacy for Hidden Leaf too!" Pausing, the Third's tone grew heavier, "You should know full well what those eyes, capable of rivaling the Mangekyo Sharingan, mean!"
"I won't fail again!"
Tsunade turned and walked away.
At the Root base…
Danzo, having received the same news, furrowed his brow.
Since information about the Koryugan was tightly sealed, Danzo didn't know Yakumo had awakened it. He was still baffled by Tsunade taking Yakumo as a disciple and risking everything to force a First's cell transplant surgery on her.
"Tsunade isn't Orochimaru. This isn't like her!"
With a thought, Danzo waved his hand.
*Swish, swish.*
In an instant, two Root shinobi leapt from the shadows, kneeling before Danzo. "Lord Danzo, what are your orders?"
Danzo said, "Find out why Tsunade took Kurama Yakumo as her disciple!"
"Yes!"
The two Root shinobi responded in unison, then vanished from Danzo's sight.
Danzo's face darkened as he sank into thought.
In this matter, his instincts told him something was off. But with Jiraiya and Tsunade—two of the Third's disciples—returning to the village one after another, his power in Hidden Leaf had been severely curtailed. So even if he sensed something amiss, he could only investigate in secret.
Considering the surgery's risks, Tsunade gave Yakumo a day off beforehand to spend time with her parents and see her friends.
Yakumo spent the day with her parents, and in the evening, she gathered with her peers at their usual barbecue restaurant.
"Yakumo, are you sure you'll be okay?"
"Yeah, I heard this surgery is really dangerous!"
"Do you really have to go through with it?"
Everyone chimed in, their faces full of worry.
Yakumo smiled, "Don't worry, I'll be fine!"
Sasuke snorted coldly, "Once you recover, we'll finish that spar we never completed!"
Yakumo glanced at Sasuke, then let her gaze sweep over Neji and Kimimaro before finally landing on Shinji. "After I recover, I'll challenge each of you one by one. So you geniuses better get ready!"
On a large tree outside the window…
Watching Yakumo brim with confidence at the table, Tsunade's lips curled into a grin. "I didn't pick the wrong person after all. If it's her, she'll definitely pull through this surgery!"
Clearly, Yakumo's heartfelt confidence had rubbed off on Tsunade.
But what she didn't know was that Yakumo's confidence didn't come from herself—it stemmed from her unconditional trust in her leader.
Shizune, standing nearby, said happily, "Lady Tsunade, it's been a while since I've seen you this happy!"
Tsunade's smile faded, replaced by a serious tone. "Let's head back and prepare. This surgery—we can only succeed!"