One thing always subdues another.
The scarlet Sharingan gleamed with intensity, its single tomoe spinning excitedly around the pupil. Hikari gazed at the grotesque, multi-eyed flesh orb in her hand, silently marveling.
The memory of Hashirama's cells devouring her own cells and chakra with reckless abandon was still vivid. Yet, when faced with the Sharingan, those cells were completely suppressed by its ocular power. Not only could they not consume the Sharingan's strength, but their vibrant chakra was being siphoned off by the eye instead.
"...Agh!"
The man's blood-red chest cavity gaped open, revealing a twitching heart and lungs. He was still screaming, though his tongue, now reduced to half its length, made his words unintelligible.
Annoyed by the noise, Hikari casually grabbed a rag and stuffed it into his mouth.
Shlick!
Her translucent fingernail, wrapped around a scalpel, deftly avoided the arteries and sliced a precise incision into his heart.
"Mmph~!"
His bloodshot eyes rolled back in agony.
Hikari's expression remained impassive as she cut into the heart and embedded the flesh orb into the wound. A green glow of medical ninjutsu illuminated the chest.
The pale flesh orb extended tendrils, rapidly fusing with the heart.
The ordinary blue chakra core and the vibrant green Hashirama chakra core began to permeate and merge, while the tomoe in the Sharingan spun wildly.
This man was the leader of the three Cloud Village jonin sent to assault the Leaf Village's main gate. After killing two Leaf shinobi, the other two jonin were beaten to death by reinforcements. This one, however, failed to take his own life and was captured alive with a sealing jutsu.
The interrogation team worked on him for nearly two months, but he didn't crack, even biting off his own tongue. In the end, they tortured him until his will weakened, then extracted the intel by invading his mind. Afterward, he was thrown into the Leaf Village prison—only to somehow end up as a test subject for the Root.
The green glow swiftly healed the wound.
In the center of the blood-red heart, a patch of pale cells embedded with a Sharingan began to spread. Hikari quickly manipulated the man's life force to resist the encroachment of Hashirama's cells.
Crack!
Behind her, Chihaya Tou took a big bite of an apple, her cheeks puffing out as she chewed. Watching Hikari's calm precision, admiration seeped from her eyes like juice from the fruit.
Over the past month of mentoring, Chihaya couldn't be more satisfied with her lab assistant. No matter how complex the medical ninjutsu, Hikari mastered it instantly, refined it with practice, and memorized medical texts in days, applying them flawlessly soon after.
Chihaya had once thought Yakushi Nono, with her prodigious talent, was the most gifted person she'd ever met. Every time she saw the incompetent fools in the lab, she missed her former student dearly.
But now? Danzo had found her an even more talented assistant in Hikari. Many of Root's experiments were now handled by her, leaving Chihaya to provide theoretical guidance. Life had become so much easier.
With less chakra being drained daily, Chihaya even felt she'd gained a bit of weight.
It's easy to go from frugality to luxury, but hard to go back.
She hoped this disciple would last a long time. The thought of life without Hikari was already unimaginable.
Thud, thud!
The familiar sound of a cane echoed from outside.
"Lord Danzo!"
The respectful greetings from the lab staff revealed the visitor's identity.
Clack!
The operating room door swung open. Chihaya tossed the half-eaten apple into the trash and stood to greet him.
"Lord Dan—"
The grim old man, his right eye wrapped in bandages, hobbled in with his cane and raised a hand to cut off Chihaya's formalities.
His narrow left eye squinted slightly as he watched the busy figure at the operating table, a hint of pleasure in his expression. "How's my disciple performing?"
"Absolutely perfect," Chihaya said with a shake of her head, her praise so effusive that even a rigorous researcher like her used the word "perfect." "Her chakra scalpel and mystical palm techniques rival mine. She can handle ninety percent of surgeries independently. She could walk into the Leaf Hospital and take a director's position with ease."
"Any psychological resistance?" Danzo asked.
Hikari's talent had never disappointed him. After a few pointers, her Wind Release mastery had skyrocketed. From that moment, he understood why someone so young possessed such strength.
She weighed 250 kilograms, and 240 of those were pure talent.
As Chihaya was about to respond, a violent clatter came from the operating table.
"Mmph!"
The man's body convulsed, shaking the table with a grating clank-clank.
The skin on his chest healed rapidly under medical ninjutsu, but the moment Hikari's chakra stopped, the pale Hashirama cells had already spread across his chest.
The dark skin was swiftly overtaken by the pale cells, covering his entire torso in an instant.
Hikari's eyes narrowed. At this rate, the man clearly couldn't withstand the Hashirama cells' invasion. Even with the Sharingan suppressing them, he was as good as dead.
If the cells kept growing unchecked, the three single-tomoe Sharingan would be wasted. Her chakra scalpel swiftly sliced open the chest, and Hikari yanked out the heart, now entirely composed of Hashirama cells.
Shlick!
Root-like blood vessels tugged at the heart.
"Mmph!"
The man's body arched violently, his hands clawing at the metal edges of the table.
Buzz!
The chakra scalpel severed the vessels connecting the heart. Only when it was fully detached did the man convulse twice more before going still, lifeless.
"See, my lord," Chihaya said with a smile, gesturing toward Hikari.
Hikari calmly placed the heart back into a petri dish, removed her gloves, and showed no emotion on her refined face—like a puppet without feelings.
No further evaluation from Chihaya was needed. This state perfectly met Danzo's expectations, perhaps even exceeding them.
He vaguely recalled that Hikari was a Leaf Village hero who had sacrificed herself to save countless comrades while fighting Cloud shinobi. Was it the effect of the Kotoamatsukami genjutsu, or had her true nature finally surfaced?
Her experimental methods seemed even more ruthless than Orochimaru's.
Ignoring the strange looks from Danzo and Chihaya at the door, Hikari held the petri dish, closely examining the flesh inside.
After devouring the man's energy, the Hashirama cells had grown significantly, nearly the size of an adult man's fist. The chakra core had expanded too, producing even more chakra.
The Sharingan embedded in the cells grew even redder, struggling to suppress the cells' power as it frantically absorbed their chakra to generate more ocular power.
One of the single-tomoe Sharingan spun rapidly around the pupil, forming a circle. As the ocular power deepened, a second tomoe began to emerge within it.
"It's evolving!" Chihaya's voice brimmed with excitement. Forgetting her pretense of loyalty in Danzo's presence, she hurried over to join Hikari in observing the Sharingan's advancement.
"The power of Yang is indeed the source of Yin's growth."
Confirming her hypothesis, Hikari's lips curved into an irrepressible smile.
Through the synergy of the Sage Body and the Sharingan, she finally understood the relationship between the body's Yin and Yang forces.
The most fundamental power in the human body was Yang. The versatile Yin power was derived from absorbing Yang. The soul, mental strength, and ocular techniques all stemmed from Yang's nourishment.
Thus, those with strong life forces never had weak souls. Conversely, those born with powerful souls, like Itachi Uchiha, often became frail because they absorbed too much Yang, leading to illnesses like his bloodline disease.
The Sage Body, brimming with infinite Yang power, was the foundation of Kaguya Otsutsuki's strength.
The deathly gray bones could only be borne by the boundless vitality of the Sage Body. The immense chakra of the Tailed Beasts required a Sage Body with vast chakra reserves to seal them. The unpredictable, wish-granting Mangekyo Sharingan needed the Sage Body to replenish its ocular power and alleviate fatigue.
Madara Uchiha knew this well.
Though he opened the Rinnegan by stealing Hashirama's chakra, his lack of vitality meant it took decades to nurture it, leaving him a withered husk.
Later, he transplanted the Rinnegan into Nagato, who had a Sage Body, to let his vitality gradually mature the malnourished eyes.
If Hikari's guess was correct, the Byakugan and the Sage Body likely had a similar synergy.
Perhaps the Sage Body's Yang power could be absorbed by the Byakugan to evolve it!
The Byakugan's precise control over the body and chakra might exist to regulate active cells at a microscopic level, preventing them from devouring recklessly and curbing the infinite transformation of Yang Release chakra.
Hikari's eyes lit up.
The Sharingan's ocular power in the Hashirama cells stabilized, its two mysterious tomoe halting at a 180-degree opposition, glowing scarlet.
It clicked!
Everything clicked!
As if a veil of fog had lifted, the world before Hikari burst into vibrant clarity. Two ocular techniques, two physiques, nine Tailed Beasts, bloodline limits, Yin and Yang forces—she had unraveled the connections between Kaguya's powers. The mighty ancestor of chakra held no more secrets from her.
"Why didn't the Sharingan I embedded before show this kind of change?" Chihaya circled the petri dish in Hikari's hands, her expression tinged with madness.
"The previous method of connecting the Sharingan to Hashirama cells was too crude. The synapses in the optic nerves weren't properly repaired, and the blood vessels were clogged, unable to absorb enough Yang power," Hikari explained excitedly, staring at the dish.
With the Byakugan's microscopic vision, she could spot and fix even the tiniest nerve blockages, enabling the Sharingan's evolution.
Danzo, who had been ignored for a while, watched the two experiment-obsessed researchers treat him like air as they fawned over the glass dish. Surprisingly, he wasn't upset.
He didn't care for or understand their theoretical discussions, but he grasped the results.
Hikari had somehow used Hashirama cells to evolve a single-tomoe Sharingan into a double-tomoe one.
This meant every single- and double-tomoe Sharingan had the potential to become three-tomoe—or even Mangekyo—with Hashirama cells.
Hashirama cells had always been more show than substance, yielding few results despite countless test subjects. Danzo had long wanted to abandon Chihaya's research but clung to a sliver of reluctance.
But if Hashirama cells could evolve Sharingan, everything changed.
He had plenty of Sharingan—over a hundred. If Hikari could turn them all into Mangekyo...
Who in the ninja world could stand against him?
Imagining that dreamlike scenario, Danzo licked his lips hungrily, his excitement surpassing even Hikari and Chihaya's.
As Hikari and Chihaya passionately discussed, Danzo quietly sat in Chihaya's chair, resting his cane across his thighs to avoid making noise that might disrupt their inspiration.
Drip, drip!
Blood from the dead man's chest cavity seeped out, splattering the floor in radial patterns along the table's edge.
Hikari and Chihaya fed chakra into the Hashirama cells, using medical ninjutsu to stimulate the other two Sharingan, trying to replicate the earlier success.
The grim old man leaned back, the cross-shaped scar on his chin stretching as his single eye narrowed, watching Hikari with an unreadable expression.
Drip... drip...
Sticky blood stretched into thin threads, connecting the dark floor to the table. Hikari and Chihaya finally mastered the method, successfully evolving the other two Sharingan into double-tomoe.
"It's all about the Sharingan's absorption efficiency. Hikari, you're a genius!" Chihaya's brown eyes bulged as she stared into the petri dish, locking gazes with the three scarlet Sharingan.
She and Orochimaru had once united over their shared dream of immortality but parted ways over differing philosophies. Orochimaru believed the soul could achieve immortality by escaping the body's constraints, while she believed it relied on absolute Yang power.
Hikari's experiment proved both were right.
Yin and Yang seemed opposed yet shared the same root. A soul could seize another's body to absorb Yang power, while a body's cells could endlessly generate vitality to nourish the soul.
Both paths were valid.
"Ahem!" Danzo, who had been sitting silently for ages, finally coughed to remind them of his presence as their discussion wound down.
"Lord Danzo, you're still here?" Chihaya set down the petri dish with difficulty, offering a polite smile.
"Trying to get rid of me?"
"I wouldn't dare, my lord."
Danzo snorted, knowing Chihaya's obsession with experiments. He didn't bother with her and turned to Hikari, who was still deep in thought, offering a stiff smile. "Well done. You're truly my disciple."
What's it got to do with you? I'm the one teaching her, Chihaya grumbled inwardly, keeping her head down.
"Does Sensei have any other business? The experiment's made new progress, so we'll likely be busy for the next few days—" Hikari responded casually, her mind buzzing with thoughts of Yin-Yang balance and conversion.
If extreme Yin could suppress and absorb Yang power, could controlling the extreme Yin Release chakra in the Sharingan—mimicking the filtering membrane on Hashirama cells—directly purify life force?
It felt entirely possible!
Pure Yin or Yang alone wasn't the true path. Only their combination could give rise to all creation.
The key to reversing the Eight Gates might lie here!
"Leave the experiments to Chihaya for now. I have a mission for you," Danzo said, cutting through Hikari's excitement.
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