Fusion with Hashirama Cells

Under the cold lights of the Seventh Laboratory, white steam rose from Neji's entire body. Strange red and blue veins crisscrossed beneath his skin—the battlefield left behind by the violent clash between lightning and fire chakra. His second attempt at fire-nature transformation had failed even more completely than the first. Not only had the conversion rate regressed, but the newly generated lightning-nature chakra within him had also revealed a greedy, invasive nature, like a beast that had tasted sweetness and begun actively devouring other forms of energy.

Orochimaru stood before the observation window, his golden pupils fixed on the fluctuating data on the monitor. His fingertips tapped unconsciously against the metal console. The rhythm exposed a rare confusion—Neji's chakra system mutation had surpassed the boundaries of existing theory.

"It is learning," Orochimaru finally said. His voice echoed through the intercom with a metallic edge. "Your lightning-nature chakra has developed an instinctive response similar to that of a living creature. This is not merely a change in nature. It is a sign that your chakra system is beginning to become alive."

Neji struggled upright. Sweat slid down his temples, mixed with blood, and dripped onto the floor. Panting, he raised his head. His Byakugan glimmered with a pale bluish-white light under the laboratory's harsh lamps. "Chakra is an outward manifestation of life energy... When one nature remains dominant for too long, it begins to imitate the host's vital characteristics."

Those words were like a key, unlocking something in Orochimaru's thoughts. He spun around and strode toward the cultivation tank. Inside the transparent container, a small sample of Hashirama Senju's cells visibly divided, multiplied, aged, and regenerated—a complete life cycle compressed into mere minutes. It was life force in its purest, most extreme form, the embodiment of Yang Release.

"What are you trying to say?" There was a trace of urgency in Orochimaru's voice that even he failed to notice.

Neji did not answer directly. He closed his eyes as though recalling something, then slowly spoke. "Lord Orochimaru, the intelligence you provided Konoha mentioned that the leader of the Akatsuki, Pain, possesses the legendary Rinnegan."

"So what?"

"Lord Jiraiya once took in three disciples in the Land of Rain." Neji opened his eyes and looked directly at Orochimaru. "One of them was named Nagato, and he was born with the Rinnegan. You should know that."

Orochimaru's pupils contracted slightly. Of course he knew. Back then, Jiraiya had smugly bragged to everyone that he had taken in three gifted children. One of them, the red-haired Nagato, had possessed the legendary Rinnegan. Later, the boy had disappeared, and Jiraiya had searched for him for years.

"Nagato was an orphan of the Uzumaki Clan," Neji continued, speaking every word clearly and carefully. "The Uzumaki Clan is known for its immense vitality and chakra reserves. According to your research, they are distant relatives of the Senju Clan and both inherited the Sage of Six Paths' Sage Body—the traits of Yang Release."

He paused, allowing the information to settle in Orochimaru's mind before raising the crucial question. "Why would a child born with an exceptionally powerful Yang Release constitution also possess the ultimate Yin Release ocular technique? Is that not contradictory?"

The laboratory fell into brief silence.

Orochimaru's fingers stopped against the cultivation tank's glass. Through the container, he could see the cells multiplying madly. His mind raced—the Uzumaki Clan's Yang Release constitution, the Rinnegan's Yin Release ocular technique, both existing within the same person...

"Unless," Orochimaru said slowly, his voice trembling with the excitement of a researcher discovering a new theory, "those eyes were not innate. They were transplanted. They came from something... that possessed both ultimate Yin Release and Yang Release."

Neji's heart tightened, but his expression did not change. He guided him without spelling it out.

"The Uchiha Clan's Kekkei Genkai is the pinnacle of Yin Release," Orochimaru continued, seemingly sorting through his own thoughts. "The constitutions of the Senju Clan and Uzumaki Clan are the pinnacle of Yang Release. If there were someone capable of accommodating both powers at once..."

He suddenly turned around, his golden pupils locking onto Neji. "Yin-Yang balance! Awakening the Rinnegan may require perfect balance between Yin-Yang Release within the same body! Nagato was merely a vessel. The true source of those eyes was—"

He did not continue, but Neji knew he had reached the conclusion: Madara Uchiha. That legendary figure who had fought Hashirama Senju at the Valley of the End—if he had truly survived, if he had truly obtained Hashirama Cells...

"An interesting deduction." Orochimaru smiled, dangerous and captivating. "So you are trying to tell me that the Hyuga Clan's Byakugan is likewise a Yin Release Kekkei Genkai. If the Sharingan can evolve through Yin-Yang balance, then perhaps the Byakugan also possesses a higher form?"

"It is only a conjecture," Neji said cautiously. "But the experiment just now gave me a clue—Yang Release has a suppressive effect on the Caged Bird."

He raised his hand and pointed to the curse mark on his forehead. "When my lightning-nature chakra went berserk and my chakra system was at its most chaotic, I felt the curse mark recoil briefly. It lasted only an instant, but it was not being suppressed. It was more like... it had encountered a force that countered it."

Orochimaru quickly walked to the monitoring terminal and pulled up the complete data from the experiment. His fingers slid rapidly across the screen before stopping on a particular waveform—the record of the Caged Bird Seal's energy fluctuation at the moment Neji's internal chakra conflict reached its peak. The graph showed that, during the three most violent seconds of the conflict, the curse mark's activity had dropped by seventeen percent.

It had not declined smoothly. It had plunged off a cliff, like an instinctive avoidance response when faced with a natural predator.

"Yang Release restrains Yin Release bindings..." Orochimaru muttered, his eyes growing brighter. "If the Caged Bird is fundamentally a Yin Release curse mark, then the ultimate power of Yang Release may indeed neutralize or even dismantle it. But more importantly..."

He turned toward Neji. Pure longing for the unknown burned in his golden pupils. "If Yang Release can make up for what Yin Release lacks and trigger the evolution of a Kekkei Genkai, then you are not merely attempting nature transformation. You are trying to unlock the possibility of Byakugan evolution!"

Neji's heart pounded heavily in his chest, but he forced himself to remain calm. "That is only a theoretical possibility. The more practical goal for now is that Yang Release may be able to reconcile my nature conflicts. If the repulsion between different chakra natures is caused by instability of form, then Yang Release, as the source power that grants form, may be able to forcibly stabilize a multi-nature chakra system."

"You want to transplant Hashirama Cells." Orochimaru said it outright.

"Yes." Neji did not deny it. "But I do not need an organ transplant. I only need an injection of sufficiently active cells. Sage Art Chakra can serve as the medium to guide the fusion, while the chakra stored by the Strength of a Hundred can provide nourishment. If it succeeds, I will not only resolve the nature conflict, but may also verify..."

He did not finish, but Orochimaru already understood—verify whether Yin-Yang balance could trigger the Byakugan's evolution. It was an unprecedented experiment, and if it succeeded, its value would be immeasurable.

"And the risks?" Orochimaru asked, his voice returning to calm. "You should understand the invasive nature of Hashirama Cells. Yamato was the sole survivor among sixty test subjects. Even with Sage Arts and the Strength of a Hundred, your chance of success will not exceed thirty percent."

"Thirty percent is enough." Neji's voice was calm. "And I have three advantages those test subjects did not."

"Go on."

"First, Sage Art Chakra. Natural Energy can gently guide cellular fusion, something ordinary chakra cannot accomplish. Second, the immense chakra reserves of the Strength of a Hundred can support the enormous energy consumption required for cell growth. Third..." Neji paused. "The Caged Bird."

Orochimaru raised a brow.

"The curse mark binds my soul, but it has also made my mental structure exceptionally stable." Neji pointed to his forehead. "The erosion of Hashirama Cells is not merely physical. It also involves mental assimilation. But the Caged Bird is like a layer of mental armor. It can help me preserve the bottom line of my self-awareness."

A long silence followed.

Orochimaru paced through the laboratory, his pale fingers unconsciously tapping against the metal console. He was calculating, weighing, assessing the value and risks of this experiment.

Ten minutes later, he stopped.

"Very well," Orochimaru finally said. "But I require an exchange of sufficient value. Hashirama Cells are one of my precious collections. Transplanting them into you means consuming an irreplaceable sample."

"What can I offer you?" Neji asked.

Orochimaru walked to the encrypted terminal and brought up a blank experimental agreement. "Three conditions. First, all data from the transplant process will be fully accessible to me. Second, if the experiment succeeds, I will have research access to any new ability you evolve. Third..."

He turned around, his golden pupils fixed on Neji. "If the Byakugan truly evolves, I want to know what it becomes, and... how to reproduce it."

Neji fell silent for several seconds before nodding. "Deal."

"Then the operation will be in three days." Orochimaru removed a transparent container from the refrigerated cabinet. A thumbnail-sized piece of pale pink flesh floated within it. "For these three days, you must continuously soak the sample in Sage Art Chakra so that Natural Energy and Yang Release can develop affinity. Six hours every day, without interruption."

Neji accepted the container. Even through the glass, he could feel the immense life force pulsing within, like a sleeping heart.

"Also," Orochimaru added, "stop all nature transformation experiments. You need to restore your body to peak condition. The pain of a cell transplant will be ten times worse than any training you have ever endured."

"Understood."

Over the next three days, Neji's life became a precise cycle.

Every morning at four, he began the Sage Art Chakra infusion. The process seemed tranquil, but it was actually perilous—too little Natural Energy could not suppress the invasive nature of Hashirama Cells, while too much would damage their vitality. He had to maintain a delicate balance within a narrow safety margin. Every infusion left him feeling as though he had fought a brutal battle.

Between infusions, he forced himself to rest, eat, and store chakra. The sealing formula of the Strength of a Hundred heated his forehead, a sign that chakra was being continuously compressed and stored. He could feel that the reserves within the seal had reached an astonishing amount, enough to sustain three days and three nights of high-intensity combat.

But observation was even more important.

As Sage Art Chakra and Hashirama Cells blended, Neji continuously observed the changes at the cellular level with his Byakugan. He saw the cells' mitochondria adjust their activity under the infusion of Natural Energy. He saw the receptors on their membranes change subtly. He saw a deeper... resonance at the level of genetic material.

On the evening of the third day, when the infusion ended, the cell sample in the container had become a smooth jade-white. Its vitality remained immense, but it was no longer violent.

After examining it, Orochimaru nodded in satisfaction. "Affinity has reached eighty-nine percent, exceeding expectations. Rest well tonight. The operation is tomorrow."

That night, Neji did not sleep.

Lying in bed, he opened his Byakugan in the darkness and examined his body over and over. Lightning-nature chakra flowed quietly through his chakra pathways. The area where fire-nature conversion had taken place still ached faintly. Sage Art Chakra, like a warm river, nourished every cell.

And the Caged Bird Seal on his forehead still lurked there, cold and sinister.

"Tomorrow..." he murmured.

If he succeeded, he might find a way to reconcile his nature conflict and perhaps even touch the threshold of Byakugan evolution.

If he failed, he would become petrified wood, collapse, or be devoured by Hashirama Cells and turned into a mindless plant-like monster.

A thirty percent chance.

Neji closed his eyes and stopped thinking. He had made every preparation he could and calculated everything that could be calculated. All that remained was to gamble.

On the day of the operation, the atmosphere in the Seventh Laboratory was as solemn as a funeral parlor.

Neji was secured to a specially made restraint chair, alloy shackles locking down his entire body. This was not imprisonment. It was protection—Orochimaru had seen too many test subjects tear out their own throats in unbearable agony.

When the injection needle pierced the spot three centimeters above his chest, Neji did not even feel pain—the anesthetic had already taken effect. But the instant the liquid entered his body, the barrier was broken.

It was not pain. It was the weight of life itself.

Hashirama Cells surged through his major blood vessels. Wherever they passed, Neji's own cells first resisted fiercely, then slowly began accepting them under the guidance of Sage Art Chakra. His skin rapidly reddened and heated up. Woody patterns surfaced around the injection point—light brown, fine as tree rings.

"First stage stable." Orochimaru stared at the monitor. "Woodification radius: four centimeters. No spread. Conflict index: thirty-one. Safe."

But safety lasted only three hours.

During the second injection, Hashirama Cells had already become familiar with the host environment. The woodification radius expanded to twelve centimeters, spreading from Neji's chest to his left shoulder. Worse still was the chakra conflict—his lightning nature, like a beast whose territory had been invaded, frantically attacked the Yang Release flowing through him.

"Conflict index: forty-six!" Tension entered Orochimaru's voice. "Neji, forcefully guide it with Sage Arts! Establish a buffer zone!"

Neji gritted his teeth and nearly drained every last trace of Sage Art Chakra from his abdomen. Natural Energy surged forth like a flood, building an isolation layer between lightning nature and Yang Release.

The tug-of-war lasted six hours. By its end, the blood Neji coughed up contained woody fibers, and the entire left half of his body had gone numb. Yet the fusion rate had reached fifty-eight percent.

The third injection was true hell.

This time, Hashirama Cells no longer invaded. They began assimilating him. Woodification spread across his entire upper body. Neji could feel his internal organs being altered—his heartbeat grew heavy and slow, the structure of his lungs changed, and every breath carried the damp scent of vegetation.

Most terrifying of all was the erosion of his consciousness. For several moments, Neji heard the whispers of trees and felt an urge to sink roots into the earth and stretch branches and leaves toward the sky.

"Hold on!" Orochimaru's voice seemed to come from far away. "Fusion rate: eighty-seven percent! Use your will and tell those cells who the master is!"

Neji closed his eyes and sank deep into his consciousness.

There, he found the imprint the Caged Bird Seal had left upon his soul—cold, binding, yet also a part of him. He actively invoked the curse mark, not to harm himself, but to use that cold power to oppose the warm expansion of Yang Release.

Yin and Yang, bondage and freedom, waged their final war within his body.

He did not know how long it lasted before balance suddenly descended.

The woodification stopped spreading. The bark-like patterns began to soften and fade, reverting to human skin—though faint brown marks remained. His heart resumed its normal rhythm, and his lungs returned to flesh and blood.

Within his body, the lightning and fire chakra finally calmed, slowly blending under the harmonizing power of Yang Release.

"Fusion rate... one hundred percent." Orochimaru's voice carried awe. "Rejection response: zero. Chakra system stability: ninety-six. Neji, you have made history."

When the shackles were released, Neji slumped in the chair without even the strength to breathe. Yet he could feel a warm, immense force within his body, like a spring that would never run dry.

Yang Release fusion was complete.

During the week-long recovery period, changes quietly took place.

First, the conflict between his chakra natures eased significantly. When Neji tested it, the conversion from lightning nature to fire nature became several times smoother, and the rejection response dropped by more than seventy percent. Yang Release was like a universal adhesive, allowing different chakra natures to coexist peacefully.

Second came the subtle evolution of his Byakugan. It was not a change in form, but an enhancement of perception—he could see the flow patterns of Natural Energy in the air and sense fluctuations in the strength of life energy. His field of vision had widened by roughly fifteen percent, a qualitative leap in actual combat.

What excited Orochimaru most was that, during a test on the seventh day, when Neji simultaneously activated Yang Release and the Byakugan, the monitoring instruments captured an unprecedented energy waveform—it was neither pure Yin Release nor pure Yang Release, but something between them, something higher.

"This is a sign of evolution." Orochimaru stared at the waveform, fanaticism burning in his golden pupils. "Yin-Yang Power is beginning to merge within your ocular technique system. It is still weak, but the direction is clear."

Neji stood in the center of the laboratory, feeling the changes within himself. Yang Release flowed warmly, Sage Art Chakra was deep and heavy, and lightning and fire natures coexisted quietly. The Caged Bird Seal on his forehead remained, but its cold sense of restraint had weakened—it was not being suppressed; Yang Release was continuously neutralizing its corrosive nature.

He raised his hand, palm upward.

With a slight thought, azure lightning flickered above his palm. With another, the lightning transformed into blazing flame. The conversion between the two natures was as natural as breathing.

Then he attempted a third thing—injecting a thread of Yang Release into his Byakugan.

The world before him changed.

It was not that his vision widened. He saw things on a more fundamental level. He saw the precise distribution of chakra within Orochimaru's body, the varying strength of life energy in the cultivation tanks beyond the laboratory walls, and even... tiny golden points of Yang Release floating through the air.

It lasted only three seconds, and the expenditure was immense.

But those three seconds let him see the possibilities.

"I need more systematic training." Neji lowered his hand and spoke to Orochimaru, who was waiting to record the data. "The fusion of Yang Release and the Byakugan, the acceleration of nature transformation, and... how to apply this new power in actual combat."

Orochimaru nodded and recorded quickly. "I will adjust your training plan. Also, I need more frequent monitoring for the research into Byakugan evolution. This change is too precious. Not a single detail can be missed."

Neji did not object. He knew this was a dangerous deal—Orochimaru was collecting data on his evolution and perhaps plotting something. But he needed Orochimaru's resources, knowledge, and laboratory.

Each took what he needed, keeping the other in check.

After returning to the stone chamber, Neji sat cross-legged and began examining himself inwardly.

Deep within his mental world, the golden points of light surrounding the transparent figure bound by green chains were several times more numerous than they had been a week ago. Like molten sunlight, they slowly but steadily eroded the foundation of the curse mark.

The chains remained firm, but tiny cracks had already appeared.

Neji opened his eyes and looked toward the cold walls of the stone chamber.

He had won the first gamble.

Next came the more difficult, more dangerous second step—while keeping himself from being devoured, he would deeply fuse Yang Release with the Byakugan and advance toward that theoretical endpoint of evolution...

Forward.