After leaving the hideout of Ryuzetsu and Chino, Shinji's second stop was his secret laboratory outside the village.
In the study, he began documenting.
The 'Twelve Palaces' was a newly created technique, and despite its impressive performance so far, he couldn't afford to be careless. After all, training the 'Twelve Palaces' involved all the body's vital organs, and any hidden flaws could have severe consequences.
Thus, he meticulously recorded his insights and experiences from practicing the 'Twelve Palaces,' as well as detailed observations of Ryuzetsu and Chino's progress in training it.
"So far, no significant side effects have been observed with the 'Twelve Palaces.'"
"However, when activated, the strain on various organs still requires further fine-tuning."
"It currently appears that the strain on muscles, bones, and cardiopulmonary systems is excessive, while the utilization of other organs is slightly insufficient."
"Ryuzetsu's progress in mastering the 'Twelve Palaces' is slightly ahead of Chino's."
"Once Chino awakens her Ketsuryugan and gains the ability to manipulate blood, her strength should see a significant boost."
After finishing these notes, Shinji paused, deep in thought.
"The difficulty of mastering the 'Twelve Palaces' is even greater than I anticipated. Ryuzetsu and Chino's rapid progress is likely due to the effects of 'Blue Higanbana No. 1.'"
"After a month of observation, Ryuzetsu and Chino, who were injected with 'Blue Higanbana No. 1,' have shown no abnormalities."
"Further observation is needed to determine if 'Blue Higanbana No. 1' has any hidden side effects."
After reviewing his notes, Shinji closed the notebook.
His intense focus on Ryuzetsu and Chino—teaching them the 'Twelve Palaces' and guiding them in medical ninjutsu—was because they were critical test subjects.
Whether the 'Twelve Palaces' had additional flaws or if 'Blue Higanbana No. 1' had hidden side effects would be verified through them.
Leaving the study, Shinji moved to the laboratory.
Skilled in the process, he connected various monitoring devices to his body and activated the equipment, checking the values displayed on the screen.
"As expected, all metrics are improving!" After a pause, Shinji sighed, "As expected of the Rinnegan!"
The benefits of wielding a pair of Rinnegan far exceeded his initial expectations.
Even now, the Rinnegan from Karin continued to provide him with the 'All Creation Power,' nourishing his Eternal Mangekyō Sharingan.
"What a pity…"
After a moment, Shinji sighed.
As time passed, the 'All Creation Power' provided by the Rinnegan was becoming less effective in nourishing his Eternal Mangekyō Sharingan.
This wasn't because the Rinnegan was supplying less 'All Creation Power,' but because his Eternal Mangekyō Sharingan was nearing the limit of its dojutsu power.
In reality, due to the limitations of the Eternal Mangekyō Sharingan's level, his 'Susanoo Tomoshibi' was poorly suited to harnessing the Rinnegan's full potential, unable to fully unleash its might.
This, in turn, restricted the amount of 'All Creation Power' the Rinnegan could provide, leaving his Eternal Mangekyō Sharingan perpetually approaching the peak of its dojutsu power without ever surpassing it.
It had become a vicious cycle.
"After all this adjustment and nourishment, it's time…"
As Shinji disconnected the monitoring devices from his body, he began planning his next steps.
With no further way to enhance the dojutsu power of his Eternal Mangekyō Sharingan, his next move was to proceed with the original plan: transplanting First Hokage cells.
Shinji was well aware of the dangers of the procedure.
He had spent so long preparing to maximize the dojutsu power of his Eternal Mangekyō Sharingan before the surgery to mitigate the risks.
Once the surgery began and the First Hokage cells were implanted, he would have to face it alone. Unlike Yakumo and Karin, there would be no one watching over him during the procedure, using 'Wazunagi' to ensure his safety.
As he pondered, Shinji paced to the cultivation area.
The cultivation area contained First Hokage cells, White Zetsu cells, and even Karin's cells.
Staring at the petri dishes, Shinji weighed his options.
From a safety perspective, transplanting White Zetsu cells was undoubtedly far less risky than First Hokage cells.
However, in terms of effectiveness, First Hokage cells were clearly the superior choice—especially for Shinji, who aimed to awaken the Rinnegan. The First Hokage cells contained a significant amount of Asura Ōtsutsuki's chakra, far surpassing that of White Zetsu cells.
"With the current dojutsu power of my Sharingan, even attempting to transplant First Hokage cells should keep the risks within a manageable range…" He paused, then continued to muse, "Besides, after training the 'Twelve Palaces,' my body's self-regulation capabilities have reached a new level. All aspects should be sufficient to endure the surgery."
After careful consideration, Shinji ultimately decided to proceed with transplanting First Hokage cells.
Next, he considered when to perform the surgery and whether to arrange any contingencies in case of failure.
His current physical condition was at its peak, so the surgery could be conducted at any time.
Given his recovery speed, as long as he survived the procedure, he would regain his strength within a day or two, without anyone noticing anything amiss.
The dilemma lay in whether to set up a contingency plan.
"Should I reveal my identity to Haku or Karin and have them assist with the surgery?"
The thought flashed through Shinji's mind.
But he quickly shook his head, dismissing it.
It wasn't that he didn't trust Haku or Karin, but even with their assistance during the surgery, they wouldn't play a critical role.
Only his own 'Jikibi' and 'Wazunagi,' through their soul-level connection, could precisely extract excess Yang Release chakra.
Other methods, even returning the Rinnegan to Karin and having her perform chakra extraction, couldn't accurately distinguish the Yang Release chakra that needed to be controlled.
Shinji, wielding the Rinnegan, was acutely aware of this.
In the realm of precise chakra extraction, the combination of his 'Jikibi' and 'Wazunagi' was currently the most advanced technique in the shinobi world.
Moreover, this surgery would heavily test his dojutsu power against the Yang Release chakra in the First Hokage cells. Thus, in his plan, not only could he not return the Rinnegan to Karin, but he also needed to retrieve Yakumo's 'Koryugan.'
He intended to use 'Susanoo Tomoshibi' to simultaneously wield the most powerful dojutsu in his possession—the Rinnegan and the Koryugan—to face this surgery that would challenge his dojutsu power to its limits!