In the original work, there are two ways for the Byakugan to evolve into the Tenseigan. One is through combining the chakra of the Ōtsutsuki clan with the Byakugan, and the other is by fusing many Byakugan together to form a giant Tenseigan.
Neiki's method of upgrading his Byakugan is very similar in description to the second route of Tenseigan evolution: hunting down clan members and taking their Byakugan. However, Neiki is certain his situation is unique and has nothing to do with the Tenseigan.
[Essence Collected: 1.4%]
Like a persistent case of eye floaters, this tiny line of text had been imprinted on Neiki's retina ever since he absorbed his father Hizashi's Byakugan essence. No matter where he looked, it always hovered at the top of his vision, constantly reminding him:
Collect more Byakugan essence.
Collect more Byakugan essence!
To become stronger, collect more Byakugan essence!
According to Neiki's own research, the essence he absorbs increases the purity of his Byakugan. When his Byakugan purity reaches a certain threshold—when the collected essence hits 100%—his Byakugan evolves and awakens a new ability.
For the Hyuga clan, the purity of one's Byakugan is basically determined at birth. It can be improved through training and frequent use, but the progress is painfully slow. Based on Neiki's previous training speed, he could only raise the "essence collected" by about four percent per year. That meant it would take nearly twenty years just to push his Byakugan to the next stage…
After experiencing the insane speed of advancement brought by plundering his clan members' Byakugan, normal training felt dull and meaningless by comparison.
Killing his own clan and absorbing their essence was the correct upgrade path for Neiki's Byakugan.
"At the current rate of essence collection, to advance from the third stage to the final stage, I need at least thirty pairs of mid-to-high purity Byakugan," Neiki murmured, lowering his gaze.
Given the current number of surviving Hyuga clan members, he would barely have enough even if he included those working in Konoha and those out on missions…
"I wonder if I'll still need Byakugan essence after reaching the final stage."
New Hyuga clan members needed time to grow. Right now, the original generation of Hyuga in Konoha were a dwindling resource. Sustainable "harvesting" of Byakugan essence would be a problem Neiki would have to face in the future.
For now, his priority was simple: become stronger.
Fifteen minutes later, dinner was ready. Neiki's cooking was excellent; he could make the simplest ingredients taste wonderful.
"Is this chicken?" Neji asked, staring at the only meat dish on the table.
"Pigeon," Neiki replied casually.
"Hmm?" Neji looked at him suspiciously.
Did brother knock down someone's carrier pigeon?
Neji took a bite, and his eyes lit up.
It tasted delicious.
Who cares.
"Brother, just asking… is there really no way for the branch family to counter the Cursed Seal of the Caged Bird?" Neji asked in what sounded like a casual tone as he ate.
Neiki glanced at him and answered evenly:
"What you want to know is something many Hyuga branch family members have tried to figure out throughout history. Whether it's using sealing techniques to counter the curse mark or faking their own deaths to trigger the Caged Bird and escape, they all failed. Those failed attempts are recorded in the Hyuga clan's ancestral hall to remind all branch members not to play around. You'll understand once you become a genin and earn permission to enter the ancestral hall."
"Then…" Neji's eyes flicked to the side, "is it possible there were successful cases, but the main family hid them so the branch family wouldn't copy them? The failures recorded in the ancestral hall might just be there to scare us."
"That's not impossible," Neiki smiled. "But it doesn't really matter. The Cursed Seal of the Caged Bird has been refined and perfected over thousands of years in the Hyuga clan. Even if there were successful cases, they probably depended on extreme, nearly unrepeatable methods. Otherwise, the Hyuga clan wouldn't still be chained to Konoha alone. In any case, there's currently no direct method to counter the Cursed Seal of the Caged Bird."
Neiki's tone was matter-of-fact, but Neji was thoroughly discouraged. Without a direct way to counter the Cursed Seal, how could he ever resist Ryo's oppression?
Huh?
Neji suddenly looked up.
"Then… is there an indirect way?" Sensing a crucial nuance in Neiki's words, he quickly asked.
"There is. Kill every Hyuga main family member who knows the Caged Bird's secret command," Neiki said with a smile.
"Ah—" Neji's face twisted. What kind of solution is that?
"Brother, are you joking?"
"Whether I'm joking or not, the problem would be solved, wouldn't it?"
Seeing his brother's roguish attitude, Neji bit his lip and played along. "Even if we wanted to kill the main family, wouldn't they just use the secret command on us the moment we showed any killing intent?"
"Who said you have to kill them all at once? Do it one by one, when they let their guard down," Neiki replied casually.
"How is that possible?!"
"How long would it even take to kill them one by one? Once they found out, it'd be over!"
Neji shook his head again and again. Neiki spoke as if all the main family members were pigs waiting quietly for slaughter, easily taken down one after another.
Even if it was possible, Neji's hatred of the Cursed Seal wasn't enough to support such drastic measures against the main family. Despite his resentment toward the seal and toward Ryo, he still enjoyed the benefits of being a Hyuga: free schooling, status, and countless invisible advantages.
Neji wasn't cold-blooded enough to raise a blade against the main family.
"That's just a matter of method. How would you know if you never try?" Neiki shrugged.
"Then you try," Neji muttered.
"Try? I already have," Neiki said.
"Sigh…" Neji sighed. Here he goes again.
His brother was amazing but far too reckless with his words, saying whatever he pleased. No wonder the ANBU had come to investigate him.
"Brother, it's fine to talk like this with me, but don't let the main family hear you. They'll take it seriously."
The Hyuga clan's rules had a very well-known clause: "the crime of disrespect." It covered all kinds of offences like showing disrespect to elders or branch family members disrespecting the main family.
Of course, the rule was mostly used for the latter.
Neiki just laughed it off. He had already been punished twice before. Although he'd learned to be more careful afterward, in Neji's eyes, he was still a repeat offender.
After dinner, Neiki got ready to leave.
"Brother, where are you going?" Neji asked, holding the leftover pigeon meat.
"To plant a tree," Neiki said without looking back.
Neji was speechless.
"If you don't want to say, then don't say… why 'plant a tree'…"
…
By the time Neiki finished "planting the tree," it was already late.
He arrived at the Hyuga clan's training ground.
He had only just stepped into the third stage of his Byakugan, and he wasn't sure how much his strength had improved, so he came here to test it.
He stared at his reflection.
"The change in Byakugan purity after reaching the third stage isn't very obvious."
The purity of the Byakugan was directly tied to a Hyuga's talent. His father Hizashi's Byakugan essence was the foundation of Neiki's rise. After absorbing the Byakugan of many clan members and reaching the third stage, his Byakugan purity was so high his eyes looked misty and hazy, adding an eerie charm to his already handsome face.
Drawing his short blade, he noticed that while the visible bloodstains had been roughly wiped off, a faint metallic scent still clung to the weapon—a flaw easily detectable by the Inuzuka clan and their ninken. Unsheathing it in front of them would require several layers of cover-up and misdirection.
Using Gentle Fist to kill was too distinctive and easy to trace. A blade, on the other hand, was clean and left far fewer clues.
"After I absorbed Hizashi's Byakugan essence, my Byakugan purity rose by one level. My dynamic vision improved, my perception became sharper, my field of view broadened, and I gained my first special ability—Insight."
The Byakugan naturally had "insight": it could see through obstacles and detect people behind walls, but it couldn't identify who they were and only presented the world in ghostly monochrome.
Neiki's Insight was different. His Byakugan saw the world in colour. He could instantly identify the people behind obstacles and was completely immune to visual-based genjutsu and ninjutsu. This ability laid the foundation for his status as one of Konoha's Twin Prodigies, capable of standing as an equal to the genjutsu genius Uchiha Itachi.
"Byakugan."
Veins bulged at his temples as his eyes sharpened. Neiki sliced through the mechanism's trigger rope, instantly setting off dozens of preset traps. Kunai shot toward him from every direction.
This kind of trap could easily take the lives of most chunin, and even many jonin would be killed if they weren't allowed to use ninjutsu.
But in Neiki's eyes, the incoming kunai seemed slow, riddled with flaws, with wide gaps in-between.
He didn't move his feet. His expression remained calm as his short blade swung, intercepting each kunai precisely at its tip. The blade's shadow danced like flowing water; his entire movement was smooth and unbroken.
The air rang with the rapid clanging of steel.
Moments later, Neiki had deflected the entire storm of kunai.
"The speed at which I spot weaknesses has increased…
…by at least thirty percent compared to the second stage," Neiki said with a satisfied smile.
Forget Gentle Fist—swordsmanship combined with the Byakugan was the perfect pairing.
"The second stage of the Byakugan gave me the ability to Analyze."
Neiki opened his hand. Lightning gathered in his palm—Konoha's version of the Copy Ninja Kakashi's signature move, Chidori.
Then the lightning vanished, replaced by a rapidly spinning sphere of chakra—the Rasengan created by the Fourth Hokage.
Fire, earth, and water-release ninjutsu followed, one after another.
Neiki wasn't a "natural genius," but his Analyze ability let him fully grasp the operating principles of a ninjutsu, and once that happened, imitating it was inevitable.
Of course, since his chakra nature was lightning, only Chidori and the non-elemental Rasengan were truly practical in battle. The other copied ninjutsu weren't as effective for him.
Analyzing and replicating the formulae of ninjutsu was just one small facet of Analyze.
Most importantly, Analyze allowed Neiki to quantify everything he saw. The degree of analysis was equal to his degree of mastery, and once analysis hit one hundred percent, so did his mastery. No ninjutsu— not even those he created himself—could escape being broken down by this ability.
Yes. As long as he could design the basic framework of a technique, no matter how difficult it was to learn, given enough time, Neiki would eventually master it. Whether it was actually useful in a fight was a separate matter.
The more difficult the ninjutsu, the longer it took to Analyze. Over the years, Neiki had created and mastered seventeen ninjutsu, ten genjutsu, and eight sword techniques. Not all of them were combat-efficient, but one S-rank genjutsu—capable of deceiving every sense and overwriting an enemy's reality—held immense strategic value.
He called it Infernal Mirage.
Testing Analyze directly wasn't easy. At the moment, only one analysis process was still ongoing:
[Analyzing: Phantom Sword (Sword Technique)][Difficulty: S-rank][Analysis Progress: 41.4%]
The progress rose slowly. At this pace, it would take at least a month to complete, though the speed had already increased by about fifteen percent compared to the second stage.
Once finished, Phantom Sword would be Neiki's second S-rank technique, after Infernal Mirage.
"The third stage of the Byakugan gave me the ability to… Replicate."
Neiki frowned slightly. He had only just completed the third stage of evolution, and this new ability remained untested.
No matter. Time to experiment.
"Byakugan."
His pupils glowed faintly blue. Neiki focused on the short blade in front of him, and the Analyze ability roared into overdrive.
[Analyzing: Standard Short Blade][Difficulty: D-rank][Analysis Progress: 20%…]
The progress bar climbed rapidly to fifty-five percent—and then, in a blink, hit one hundred percent.
[Analysis Complete!]
Fog-like chakra condensed in the air. Under Neiki's handsigns, the mist was drawn inward like a black hole, surging into a single point.
The next second, the chakra mist dissipated, leaving behind an identical short blade resting on the table.
Neiki examined the two blades closely, his expression turning serious.
This wasn't a shadow clone. It was actual, physical matter.
There was no difference—none at all. Even the faint, metallic smell of blood was identical.
"Replication… creating something from nothing. This is Yin–Yang Release," Neiki thought, feeling the sharp drain on his chakra and letting out a wry smile.
This wasn't like Kakashi's famous copying ability. This was forging the tangible from the intangible, far surpassing the Sharingan. Replicating inanimate objects was clearly possible—and living beings might not be impossible either. As long as something could be Analyzed, it could theoretically be Replicated, limited only by his chakra reserves.
The technique wasn't directly offensive, but the power to pull form out of nothingness—to create anything—was the very domain of Yin–Yang Release, the power once wielded by the Sage of Six Paths.
With Replicate, the possibilities were endless.
Countless ideas flickered through Neiki's mind, but in the end, he took a deep breath and forced himself to calm down.
Replicating a single short blade had already consumed more than half of his chakra. Any grand plan would first have to solve the problem of his chakra capacity.
"For now, the priority is to advance my Byakugan to the final stage."
Who knew what the highest level of the Byakugan would awaken?
At that moment, footsteps sounded at the door.
"Neiki, the clan head wants to see you."
PS :
The Tenseigan, is a powerful dōjutsu (eye technique) from the Ōtsutsuki clan
Tenseigan (Canon) – An advanced dojutsu evolving from the Byakugan.
Two known canon routes:
Combining Ōtsutsuki chakra with the Byakugan.
Fusing many Byakugan into a giant Tenseigan.