Chapter 58: Black Zetsu's Unfortunate Experience
Aizen's arrangement with Uchiha Madara was comprehensive—though not without its reservations.
Aizen had always regarded this living legend of the shinobi world with a measure of respect. After all, a master was still a master. Even if the man knew nothing of Kidō or reiatsu, his understanding of chakra and warfare made him worthy of acknowledgment.
As for Madara himself—well, to put it politely, he was soft-hearted. To put it less kindly, he was easily manipulated. Though he was perfectly aware that Aizen found his ideals laughable, Madara still maintained a curious sense of respect for him, impressed by Aizen's courtesy and his willingness to share information and resources.
Of course, their communication had never been direct. Madara preferred to operate through Uchiha Kagami as an intermediary. Aizen, ever the patient schemer, tolerated this inconvenience with practiced grace. The aging Uchiha, half a step from the grave, still harbored suspicion that Aizen might one day turn against him—even though Aizen had no such intention.
This exchange was no different.
Aizen provided Madara with his research on the internal binding principles of the Shinigami System—the structure of spiritual restraint and reiryoku control. In response, Madara decided to display his mastery of Yin-Yang Release.
Not because he was jealous of Aizen's genius, of course—he simply wanted to demonstrate the dignity of an elder.
The result was almost fatal.
Madara very nearly killed himself in the process, but by some miracle, he succeeded. The outcome of that reckless experiment was the creation of Black Zetsu.
This half-black, half-white being claimed to be a fragment of Madara's own soul. It possessed knowledge of lost eras, fragments of research data, and the ability to manifest the White Zetsu, a byproduct of cellular mutation.
As the first successful product of Madara's Yin-Yang Release, he was quite satisfied—pleased enough to boast about his achievement. Black Zetsu, ever the opportunist, played the role of a dutiful subordinate, praising his "father's" divine intellect and legendary vision.
And then, without hesitation, Madara threw him straight into Aizen's hands as a living research specimen.
Both parties were content with the trade.
Aizen gained a rare, chakra-based life form born from Yin-Yang Release, while Madara obtained a complete set of Aizen's research notes on the Ninety-Nine Forbidden Bindings and the final technique—Bankai: Taisei.
To Aizen, these were old, deconstructed theories—nothing more than discarded frameworks from a bygone study. He had long since dismantled and restructured every Kidō from the Fudō series; offering Madara these papers was like tossing an outdated blueprint in exchange for a glimpse of living chakra.
Of course, Madara wasn't without his own tricks. The wily old man laced Black Zetsu with safeguards and deceit. Aizen's research could only extract data from the being's physical form—he could not access the true theoretical workings of Yin-Yang Release. Madara had refused to record the principles, claiming he was "too tired to write."
And so, both men left the exchange feeling simultaneously satisfied and cheated—each convinced that the other had revealed just enough to remain useful.
Neither of them spared a thought for Black Zetsu.
But he certainly had thoughts.
Far too many.
Because Black Zetsu was not Madara's split soul at all.
He was a living construct of chakra—an ancient being born from a far greater existence. He was the will of Kaguya Ōtsutsuki, the Rabbit Goddess herself—the third child she trusted above all others, born to free her from her prison beneath the moon.
For a thousand years, he had endured.
For a thousand years, he had schemed, whispering into the ears of mortals, manipulating bloodlines and wars—all for the single purpose of restoring his mother.
And now? Now he had been gifted away like a lab rat.
This can't be real.
Black Zetsu was furious. His thousand-year effort had culminated in servitude to two lunatics—one a delusional corpse clinging to a dream of peace through illusion, and the other a godlike manipulator dissecting souls for curiosity's sake.
He had been the one to save Madara's life, to repair his frail body, to infuse his cells with chakra and stave off death again and again. Every cell, every pulse of chakra in Madara's body had been rebuilt by his own effort—all so the old fool would continue to trust him.
And this was his reward?
To be thrown into a lab and dissected by Aizen Sosuke?
The indignity burned deeper than any wound.
But the worst part was Aizen himself.
That man was wrong—utterly wrong.
He must have known. He must have seen through the lie—that Black Zetsu was no mere construct of Madara's chakra—but he said nothing. He didn't even ask.
No mocking questions. No probing curiosity.
Just silent, methodical examination.
He cut him apart as though he were nothing more than raw material.
Why won't you ask? Black Zetsu screamed internally. Why don't you want to know what I am? Don't you care what you're cutting open?
Surely, a true researcher would have shown curiosity. Surely, a being who sought the truth of the world would want to know about chakra's origin—about the truth buried beneath a thousand years of war.
Black Zetsu tried to appeal to reason.
"I have knowledge," he said hurriedly during the examination. "The memories I carry differ from what Madara has given you. I have glimpsed the primordial essence of chakra itself—truths buried in the world's energy, truths that could reshape the shinobi world forever."
Black Zetsu was an eloquent manipulator, well versed in the psychology of mankind. He knew how easily humans could twist themselves for the sake of lofty ideals like world peace. People obsessed with chakra were particularly vulnerable to such grand promises.
So he crafted a story—a perfect bait—tailored for an intellect like Aizen's. He waited for the man to stop cutting and ask questions. He waited for that familiar flicker of curiosity, for the desire to probe into mysteries beyond comprehension.
And then Aizen finally replied.
He didn't care.
He said it calmly, as if stating the weather.
He didn't care about world peace.
He didn't care about lost history.
He didn't care about divine truths or salvation.
Aizen simply said that he preferred to research step by step—to reach the truth through method, not revelation.
"The correct approach to research," Aizen had remarked, "is to complete the results first—then verify them against the original information, not the other way around."
At that moment, Black Zetsu realized something horrifying.
He had fallen into the hands of a true madman. Not just any madman, but one whose insanity transcended the understanding of the entire shinobi world.
Mother, forgive me for my failure. I cannot save you. Uchiha Madara, at least, is a lunatic whose madness I can comprehend. But Aizen Sosuke—his mind is beyond reason.
"...This Mr. Black Zetsu is a special life form created through Yin-Yang Release," Aizen announced from the podium, smiling with practiced gentleness. "If you need materials for research—flesh, blood, or genetic samples—you may request them from him directly. Whether it's tissue fragments or full-body constructs, Black Zetsu will provide them."
His tone was friendly, almost domestic—like a butcher describing his freshest cut.
From below the stage, Tsunade stared at the miserable creature with pity. His face looked as though he had already died inside. For a moment, her conscience stirred. She wanted to speak up—to stop this.
But then she heard Aizen's next words: a life form created through Yin-Yang Release... unlimited regenerative flesh and blood.
Her medical instincts twitched.
A renewable biological source… endless tissue samples… no ethical limits… I could save countless lives…
Slowly, Tsunade lowered her hand and turned away under Black Zetsu's hopeless gaze.
It wasn't cruelty—it was practicality. In the world of shinobi, chakra-born beings weren't truly considered human. The tailed beasts were proof of that. They could think, feel, and speak, but in the end, they were still classified as tools of war.
And if they can't feel pain, what harm is there in cutting them open?
Besides, the opportunity was too tempting.
As a medical ninja, Tsunade knew this was a once-in-a-lifetime chance. A chakra lifeform sustained by Yin-Yang Release offered endless data—regenerative cells, binding patterns, transmutation reactions. She could revolutionize medical ninjutsu.
She thought of herself—not as a saint, but as a sinner among sinners.
If I were truly righteous, would I gamble away my fortune? Would I abandon Konoha after losing faith in it?
No, she decided. This wasn't betrayal. It was understanding reality.
At worst, I'll learn what I can, record my findings on Yin-Yang Release and tailed beast physiology, and leave the results behind for Konoha. That, too, is the Will of Fire.
The thought made her strangely calm.
When she recalled Hatake Sakumo's moment of defiance—the "Bible-breaking" incident—she even smiled faintly.
Turning back to the podium, she watched Black Zetsu, now looking more like a trapped animal than a god's emissary.
"…Can I return to my master?" Black Zetsu asked softly. "I promise not to appear before anyone again."
His voice trembled as the surrounding ninjas exchanged strange looks.
Aizen, already tidying up his notes and scrolls, didn't even glance at him.
"I'll tell you whatever secrets I hold," Black Zetsu begged. "Conduct your research, but at least put me somewhere… normal. Or give me a few days to prepare myself mentally."
"How could you think like that?" Aizen replied gently, genuinely puzzled. "Didn't Uchiha Madara send you to aid in our great endeavor? You can divide yourself infinitely—surely that ability was meant to serve the progress of this world. Besides, Madara has already granted permission to use you freely. Don't worry… you will become part of history."
Without another word, Aizen turned and left, his footsteps echoing through the sealed corridor.
As the heavy doors shut, Tsunade and the others stood silently for a moment. Then, as understanding dawned, a low murmur spread through the researchers.
So the other collaborator… is Uchiha Madara.
Shocking, yes—but not unexpected.
While thoughts churned in their minds, Tsunade's eyes glowed faintly blue. A chakra scalpel flickered to life in her hand.
All around her, other members of the Chakra Research and Flesh Analysis Departments followed suit, activating their light blades with quiet precision.
They exchanged solemn nods, the room suddenly filled with an eerie brilliance.
Black Zetsu froze.
"Mr. Black Zetsu," one of them asked politely, smiling behind his mask, "will you be splitting yourself… or shall we do the honors?"
"…Can I choose another option?"
"No."
The scalpels flared brighter.
Their smiles did too.
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