After completing the experiment, Shinji and Yakumo left the laboratory and headed toward the shinobi academy.
"I never expected the flesh and blood of those monsters to contain such terrifying power. Even the most potent poisons we've collected can't completely destroy their cellular tissue…" Yakumo couldn't help but marvel as they walked.
For the past few days, Tsunade's experiments had focused on countering the regenerative abilities of demons.
After all, during the great battle in the Land of Grass, though the 'Upper String' had been defeated, 'Upper String One,' 'Upper String Two,' 'Upper String Three,' and that mysterious figure with terrifying strength had only vanished without confirmed deaths. The village had to prepare for the possibility of the 'Upper String' making a comeback.
Thus, finding a way to counter the demons' flesh regeneration became the top priority for Tsunade's research team.
"Indeed," Shinji sighed softly.
Honestly, the raw data had shocked him too, given the demons' regenerative capabilities.
Even the First Hokage, renowned for the most formidable regeneration in the shinobi world, only theoretically possessed limb-regeneration potential. The hidden cost of such rapid regeneration was evident in the First's early death.
But demons were different.
Leaving aside the high-ranking 'Upper String' demons, even ordinary demons could effortlessly regenerate limbs.
Moreover, demons had extraordinarily long lifespans.
As long as they consumed fresh flesh and blood, they could sustain their lives almost indefinitely.
Shinji recalled that in the original Demon Slayer timeline, Muzan Kibutsuji, imbued with the power of the Demon King, aged nearly nine thousand years after being hit with an aging drug and still didn't die immediately.
Nine thousand years!
Forget everything else—that lifespan alone could outshine the 'Sage of the Six Paths.' Perhaps only Kaguya Otsutsuki, sealed on the moon as the 'Goddess of the Rabbit,' could rival it in the shinobi world.
So, in all honesty, the most precious treasure of the Demon Slayer world wasn't the swordsmen's breathing techniques or the special abilities that pushed human limits and unlocked selfless states.
The greatest treasure of the Demon Slayer world was the near-invincible power of demonic flesh!
Soon, the two arrived at the shinobi academy and returned to their respective classes.
During class, Shinji's mind wandered, mentally reviewing the counter-strategies Tsunade had developed specifically for demonic flesh.
The fact that demons feared sunlight was no secret.
With this lead, Tsunade's poisons had rapidly improved in potency. Shinji believed that given a bit more time, she'd develop a poison capable of countering demons.
His secret laboratory had the capacity to replicate any drug. Once Tsunade made a breakthrough, he could immediately reproduce it.
That evening, outside the Hidden Leaf Village.
Swish.
A figure landed in the forest, glancing around cautiously.
Karin emerged from behind a large tree, calling out to the figure, "I'm here!"
Seeing Karin, the figure hurried over, lowering their voice in a respectful bow. "Leader!"
Karin said, "Ryuzetsu, no need to worry—there's no one nearby!"
The person sneaking out to meet Karin was none other than Ryuran's sister, Ryuzetsu.
Ryuran didn't trust anyone else with such a task.
Having learned from her brother that Karin was the true leader of the village and possessed strength surpassing a Jonin, Ryuzetsu relaxed upon hearing there was no one around. Steadying herself, she reported, "Leader, the Anbu received intelligence that the five great shinobi villages are secretly collecting various poisons and toxins, purpose unknown!"
Karin nodded slightly, signaling Ryuzetsu to continue.
Ryuzetsu added, "Elder Mitsuzawa, who was sent to investigate the whereabouts of the 'Box of Ultimate Bliss,' has been missing for days. Brother is worried he may have met with an accident!"
Karin paused, feigning contemplation, before saying, "For now, abandon the investigation into the 'Box of Ultimate Bliss.'"
"Yes!"
Ryuzetsu nodded.
As a member of the 'Flower of Grass' faction, she had no fondness for the 'Box of Ultimate Bliss.' In her eyes, it only brought disaster to the village.
After sending Ryuzetsu away, Karin headed to the secret laboratory to report the intelligence gathered by Grass Shinobi Village to Shinji.
"Collecting poisons and toxins?"
Shinji was momentarily stunned, then gave a wry smile.
Clearly, the Hidden Leaf wasn't the only village targeting demons. The other four great shinobi villages were likely conducting their own secret research on demons. Given how many demons the mysterious figure released during the Land of Grass battle, it wasn't surprising that other villages had captured one or two.
Like Tsunade, the other villages were probably focusing on countering the demons' rapid regeneration, hence the large-scale collection of poisons and toxins.
"Now the entire shinobi world is racing to study the demons' weaknesses. It won't be long before results emerge!"
With that thought, Shinji turned to Karin and instructed, "Go back and prepare. Chakra will be transferred soon."
"Understood!"
Karin nodded and left.
After calibrating the lab's equipment, Shinji left the laboratory and quietly returned to the Hidden Leaf, back to his apartment.
After a quick wash, he sat on his bed, activated Jikibi, and contacted Sasuke.
Sasuke, reached by his leader, eagerly asked about his doubts regarding the Eternal Mangekyo Sharingan.
After probing a bit and learning Sasuke had heard about the Eternal Mangekyo Sharingan from Itachi, Shinji marveled at Itachi's meticulousness while answering, "You guessed right. Both I and 'B' possess the Eternal Mangekyo Sharingan!"
"What!?"
Sasuke couldn't hide his shock.
Truthfully, he had been resistant to the idea that something like the Eternal Mangekyo Sharingan existed beyond the Mangekyo Sharingan.
Even with mental preparation, the confirmation still stunned him.
Shinji mused for a moment before saying, "Do you know why Itachi spared your life?"
Sasuke hurriedly asked, "Why?"
Shinji said slowly, "Because advancing to the Eternal Mangekyo Sharingan requires a pair of Mangekyo Sharingan from a blood relative! And your eyes are what Itachi needs!"
"So that's how it is…"
Sasuke's tone grew cold.
Shinji paid no mind to Sasuke's emotional state and instructed, "Tonight, I'll absorb your chakra. Be ready!"
Due to the Land of Grass battle, his 'Rinnegan Plan' had been delayed for some time. With the mysterious figure temporarily repelled, he needed to accelerate the plan, aiming to possess at least one pair of Rinnegan by the time they counterattacked the Demon Slayer world.