Kimimaro understood the Byakugan far more deeply now than most Hyūga, at least than those alive today, he felt, thanks to recent years of focused research already and the fragments of canonical knowledge he still remembered.
Piece by piece, the two perspectives had merged into something coherent.
For once, Byakugan didn't resist manipulation the way the Sharingan did.
It adapted. It stabilized. It always wanted to integrate.
Even real historical cases supported what he found.
Mukai, that Hyūga-descended shinobi whose line had clearly branched off long before the modern clan ever joined Konoha, Kimimaro deduced this because the Hyūga's strict marriage monopoly would never allow such an "accident" afterward, had awakened a Byakugan despite being so far removed from the main clan.
Yet there was no equivalent case for the Sharingan.
Not a single one.
No one had ever awakened a lone Sharingan out of nowhere.
The reason was obvious: the Sharingan simply wasn't as adaptable or naturally emergent as the Byakugan.
The Byakugan also simply behaved better in foreign hosts.
It could activate and deactivate at will, avoiding constant chakra drain.
It didn't collapse outsiders, in all kinds of ways, the way transplanted Sharingan did, which demanded overwhelming vitality or bloodline purity just to function, as both Kakashi and Danzō had proven.
And there was Ao, an even clearer example.
Not Hyūga, not even from the same village, and yet he used the eye flawlessly, as if he had had it his entire life.
Kimimaro had seen it firsthand, too.
Through instruments, from the beginning, in the experiments, the Byakugan accepted Yang chakra easily, merged with new tissue more easily than expected, and responded to regeneration without losing function.
Everything about it screamed compatibility.
Stability. Life.
It made perfect sense.
It was tailor-made for Kimimaro to use as an edge.
The Byakugan leaned toward Yang, matter, biology, the body's reality.
The Sharingan leaned toward Yin, spirit, emotion.
Both came from the same, generally more 'Yin-like' Sage lineage, yes, Sage Eyes rather than Sage Bodies, but even within that category, spectrums existed.
The Byakugan was simply built differently from Sharingan.
That was why their clone experiments progressed so quickly.
The eye itself wanted to adapt.
Where the Sharingan's power came from the user's personal spirit and trauma, the Byakugan spread outward, linking itself to the body, the chakra network, and the life force around it.
It was broader, steadier, designed for harmony and evolution rather than obsession.
To understand it even more perfectly, Kimimaro first had to define what a dōjutsu truly was.
The original series from his past life never explained it.
Effects, yes.
But not the underlying structure.
Months and years of research into both one of the strongest Sharingan and the purest Byakugan had finally led him to the one conclusion he'd always wanted to understand.
A dōjutsu wasn't merely a genetic quirk or hereditary trick.
It was a hybrid phenomenon: part biological organ, part spiritual seal.
A living chakra construct designed to store, shape, and project power into reality through perception, using the eyes as the most logical interface.
The eye acted as a converter, a specialized projection node that refined chakra within its structure until it could manifest unique abilities directly through sight, bypassing the need for hand seals entirely.
That was why the Ōtsutsuki, after consuming chakra fruits from the God Trees, naturally manifested dōjutsu.
They needed permanent containers to hold that overwhelming chakra.
And the eyes, fastest sensory gateway to the world, became that vessel.
The Byakugan was the oldest of those eyes, the baseline template of the Ōtsutsuki.
Balanced. Efficient.
That explained everything.
Why it appeared so consistently in the Hyūga.
Why its upper limits seemed lower.
Why its growth curve was wide instead of sharp.
It wasn't weaker, just designed for universality.
Stable across hosts.
Functional in every environment.
The perfect long-term tool for a species that colonized worlds.
The Sharingan was its opposite: volatile, chakra-hungry, individualized.
Built for escalation, not consistency.
"Naturally, the Byakugan's improvement won't be as explosive as the Sharingan, directly elevating anyone to a level comparable to a Kage in one singular instance, and so easily."
"However, the Byakugan has its advantages. It doesn't consume a large amount of eye power; it only improves the ninja's foundation by always giving an organic boost to vision and chakra. It won't lose its light like the Mangekyou Sharingan."
"Stability... indeed, that's the most basic characteristic of the Byakugan."
The Rinnegan and Tenseigan were just the higher evolutions of that same system, divine eyes born from compression, fusion, or imbalance of Sage chakra.
But the Byakugan remained the root.
The ancestral interface between chakra and the material world.
That was what fascinated Kimimaro the most.
The Byakugan wasn't just an eye.
It was the Ōtsutsuki blueprint for how chakra should view reality… and how it might rewrite it, once pushed far enough and evolving.
His own period of study had also shown him something odd about its modern holders, Hamura's descendants.
Their adaptability reminded him of the Giant Tenseigan on the moon.
That enormous construct had been sparked by Hamura's own Tenseigan, yes… but why did the moon clan offer their eyes to it generation after generation?
It couldn't be symbolic alone.
The answer was simple once he saw it.
The Giant Tenseigan likely grew through the same fusion principle he and Emi were using now, multiple Byakugan merging, reinforcing each other, amplifying their collective power.
Because it worked. Effortlessly.
And that similarity bothered him.
Not just the fusion.
The system behind it.
The Hyūga's cursed seal on the Branch Family operated on disturbingly similar principles: chakra links, remote control, suppression.
A smaller, twisted reflection of the moon clan's mechanism.
A coincidence?
Kimimaro didn't believe in those.
Not in this world.
A question had come to him naturally one afternoon, while Emi was adjusting a chakra stabilizer with that focused, meticulous expression she wore when she worked.
"Where do the Byakugan go when a Hyūga dies?" Kimimaro asked quietly.
Emi blinked, caught off guard. She thought for a moment before answering.
"All Hyūga are buried in the same place," she said. "The bodies are taken immediately, guarded by a special unit of pure Main Branch descendants. Everyone goes into the main compound's central burial chamber. Even Side Branch members. It's… tradition."
"All of them?"
"Yes. Always."
He let that sit before he asked the next question.
"Have you ever heard of someone getting replacement eyes? Say, if a Side Branch member was injured?"
Emi frowned. "A few cases. I heard of injured members receiving new eyes. But the cursed seal always stayed. It didn't change anything."
That was all he needed to connect the dots.
It confirmed what he and Emi had demonstrated already, that beating the cursed seal wasn't about removing it, but overwhelming it.
Smothering it with pure Byakugan energy until the control link broke on its own.
But that burial custom revealed something far more dangerous.
The Hyūga almost certainly kept an accumulation of Byakugan stored underground, beneath the compound, passed down for generations.
Perhaps not only for replacements or to preserve elite eyes for future heirs, but for something larger. Something hidden.
Kimimaro could see the outline of it now.
The clan had likely constructed its own miniature Giant Tenseigan-like localized energy vessel beneath its grounds.
Or perhaps it was connected to it somehow externally as well.
It explained why they kept such an illogical clan structure.
Why the Main Branch held absolute control.
Why the Side Branch system continued despite being outdated.
They needed it.
But why, that remained unclear.
One thing was certain, though: without Hamura's personal Tenseigan as a core, it would be weaker than the moon construct.
But because it was stationed directly on Earth, it didn't need long-range projection. Locally, the effect could be just as powerful.
And suddenly, everything aligned.
It explained how they were able to target Emi from such a vast distance that day.
After all, Toneri could sense events on Earth from the Moon itself to a degree.
So why couldn't a lesser, earth-bound system do the same on a smaller scale?
The strange Byakugan-like energy he and Ashina couldn't identify originally…
The unnatural accuracy of the attack…
The absolute dominance the Main Branch maintained without stepping outside its walls…
The cursed seal, the burial grounds, the accumulation of eyes, they were components of the same architecture.
Only the patriarch's core bloodline, men like Hiashi, could likely access it.
The seal was not just an internal control; it was an outward anchor, capable of channeling power across vast distances.
Kimimaro had to weigh all of this. Every detail, every implication.
He had no choice.
The Hyūga were his next main target during the Konoha Crush, and he refused to walk into that battlefield blind.
He already anticipated the Hyūga to be far more troublesome than anything shown in canon, maybe even more troublesome than anything Konoha had on the surface currently.
And why hadn't they used this in the original timeline?
Simple.
They never needed to.
Konoha Crush didn't endanger them.
Pain's attack was too sudden.
And who knew what protections they secretly activated during these events, if they truly possessed such power, what else could they do?
Why hide it? Because they saw what happened to the Uchiha once they became too visible, too overtly powerful.
Let them carry the burden and apprehension of the rest of the village, instead.
And the Hyūga, with the best ocular prowess in the entire village, probably already long understood better than anyone how dangerous Konoha's rotten four elders truly were.
Danzō especially would have dissected their entire clan without a second thought if he ever suspected such a system existed.
So hiding made perfect sense.
Staying passive, compliant, outwardly overly submissive to Hiruzen and the Hokage faction wasn't loyalty at all. It was camouflage.
'Or maybe even a shield…'
Kimimaro paused at the thought, the logic unfolding too cleanly to ignore.
He now suspected something even deeper.
Something the Hyūga would never openly admit.
Not to Konoha.
Not to anyone.
Perhaps the Hyūga had been hiding behind Konoha all along, using the village as a buffer against the one threat they feared most, the Moon Clan.
Toneri's people, their cousins, after all, had every logical motive to steal Earth's Byakugan to enrich their own powerful ancestral toy.
This could be why they truly joined Konoha as well.
And yet those attempts seemingly mysteriously stopped, "on their own", long before, since they were never mentioned by anyone.
But why was that the case? Could it be tied to the Hyūga's underground vessel, this earthly countermeasure they created to bite back?
Perhaps that had been the cursed seal's original purpose, long before it was twisted by the Main Branch's elitist, parasitic indulgences.
The more he pieced together, the more it clicked.
After all, back then, didn't Hiashi seem to know an awful lot about Toneri's Moon side of things, despite never hinting at such knowledge anywhere else in the past?
Very suspicious, indeed.
And Kimimaro knew that even more pieces would maybe fall into place soon.
Once, he walked into Konoha himself very soon, as he had already agreed upon with Orochimaru.