The laboratory lay even deeper under this main hideout, half carved from stone, half built from scavenged steel and black-market components Kimimaro had acquired over the years.
The air hummed with quiet chakra-powered machinery and fuinjutsu, crude compared to true scientific facilities, but far beyond anything a typical cult could have assembled and very ingenious in its own way.
Kimimaro stood beside one of the long metal worktables, flipping through a notebook filled with tightly packed handwriting.
Page after page of diagrams, chakra flow maps, sketches of cell structures drawn from Emi's descriptions, everything he had learned since the very first day they began experimenting together. Internally, he knew the irony of it all.
Yes, he had modern knowledge from his past life. Basic biology, chemistry, and the broad strokes of genetics.
But once he introduced souls, chakra pathways, nature transformation, bloodline spiritual signatures, and Yang regeneration into the equation… that old knowledge crumbled.
Entire branches of real-world science became useless or incomplete.
He had gaps everywhere. So he had started again from the ground up.
Experiment by experiment. Sample by sample.
He had gradually bought every basic literature of interest and scientific tool available on the black market, microscopes, crude centrifuges, elemental stabilizers, chakra-reactive sensors, anything that could be smuggled quietly into this island fortress.
Over time, the laboratory expanded from a cramped shelf of tools into a full room, then into several adjoining chambers.
Many sections were even built with Ashina's invaluable indirect and Reika's direct sealing support. Yet none of it would have been truly possible without Emi first.
Beside him, she was adjusting the flow of chakra into a glass container, her Byakugan active, eyes glowing softly.
Emi wasn't just an assistant; she was the irreplaceable core of their research.
She was already like a living instrument, but when connected to the actual machines, she became even more potent, guiding, amplifying, refining.
Together, they had become something like pioneers of a new shinobi science, stitching together the biological theories Kimimaro remembered, with the mystical realities of this world that Emi could observe directly.
But even with all this progress, Kimimaro had realized a hard limit.
You couldn't reach genetics here.
Not with the current equipment.
Not with the current theory.
Not in decades of broader worldly progress.
They could analyze tissues. They could observe cells.
They could chart chakra pathways at the microscopic scale.
But the deeper blueprint, the true genetic-level structure of bloodlines, remained inaccessible. Their notes reached the edge of a cliff and could go no further.
Still, they had their first real project, finally, now, something manageable, something foundational:
Using Emi's unique and gifted Byakugan, gentle fist precision, and Yang Release proficiency to modify tissues and cells,
To engineer organelles,
To influence how cells behave,
To nudging the body toward 'improvement'.
It was crude now, the earliest stage, but it was a beginning.
A step toward a biology that mixed chakra and life into a single theoretical framework.
And beyond that?
A more distant ambition: multiplying tissues in vitro.
Growing biological material outside the body.
A stepping stone toward true modification.
Which led them to his secret and Emi's only real interest:
The Byakugan.
Her cursed seal had enslaved her for years.
Even now, it rested dormant but waiting, a shadow she had not forgotten.
Kimimaro believed that if they could push her Byakugan beyond its current limits, evolve it through some kind of biological reinforcement, the cursed seal might no longer apply to her eyes inherently, and, therefore, she would no longer need any counter-seals.
Because the Caged Bird cursed seal ultimately could not control an eye that surpassed the limits of its original design, no matter how mysterious it seemed to them currently.
But for that, they might eventually need something more.
"Stealing another Byakugan," Kimimaro said internally.
Not for power right away. But for material.
For tissue comparison and to study it better externally, after all, it was hard for Emi to dissect her own eyes, no matter how you looked at it.
For fusion.
For creating a next-stage eye for Emi someday.
Her new, evolved eyes that would allow her to twist her original fate completely.
They weren't ready yet. Not even close.
Even if they had enough power to dare to extend their hands into Konoha and the Main Branch chamber, they didn't have enough skill and experience yet.
But the theory was already slowly forming, and would be ready by a few years, perhaps.
For now, they would just continue quietly improving like always.
...
Emi leaned over the glass chamber, violet eyes glowing through the soft Byakugan activation.
Strands of chestnut hair slipped from her side ponytail as she adjusted the chakra flow with surgeon-like precision, the faintest spark of amusement on her lips.
The lab's blue-tinted light sharpened the contours of her face, giving her that mix of youth and alarming competence she always carried.
"You're making that face again." She murmured eventually, seeing him lost in thought again.
"What face."
"The one where you realize your 'brilliant theories' don't match reality and you pretend you're not annoyed."
Kimimaro didn't look up from his notes. "This world's biology is… less intuitive than expected, as I said many times."
She snorted. "You say that like you weren't somehow already halfway to inventing new fields before we even got proper microscopes. Seriously, where do you get half of this stuff?"
"From observation," he answered simply.
"Mm. Right. Observation," she echoed with a grin, fully aware that Kimimaro's instincts bordered on supernatural insight.
"But even your overclocked brain can't make genetics appear out of thin air."
"No," he said calmly. "Not any time soon, at least."
"Hey," Emi said suddenly, tapping a metal tray with the back of her knuckle, "stop acting like you're the only genius in this room."
"I'm not pretending."
She flicked him with a chakra-coated finger. "There. Now you're humble."
Kimimaro stared at her. "That did nothing."
"It did in my heart," she replied.
A few moments of silence stretched between them as she guided another chakra thread through the sample, her focus steady but her thoughts clearly drifting.
"Kimimaro…" she said at last, voice quieter than before, "do you ever think about how our lives would've gone if you didn't pull me out of that whole disaster?"
"No," he said plainly. "You'd just be dead."
"…You're terrible at comforting people."
"I'm not attempting to comfort you. I'm stating facts."
Emi exhaled a small laugh. "Well… thanks for the facts, then. And for making all this possible."
He didn't respond immediately, but the slight shift in his posture told her enough.
"You didn't die, after all..." he said. "Because we intervened in time."
"We?" she teased lightly. "It was you. Reika just watched, horrified."
"That's because she didn't know how the seal worked."
"And you did?" Emi raised a brow. "Back then, you were improvising."
"Calculated improvisation," he corrected.
She laughed softly. "You saved my life with a guess."
"A correct one."
"Well," she murmured, adjusting the glass plate, "I'm grateful either way."
She looked at him, serious for a moment.
"You really think we can do it? Evolve the Byakugan itself?"
"You've already begun the process, Emi. This research is the key..." he replied.
"But for full evolution, we'll need external samples."
Emi smirked. "Meaning a stolen Byakugan."
"So," she continued, leaning closer to him, "when are we stealing it exactly?"
"When the opportunity appears."
"That's vague."
"That's intentional."
She smirked, the corner of her mouth lifting with a sharp, vindictive satisfaction.
"Fine. Just warn me. Then we'll take it. Together. I can't wait to see the faces of those ugly Main Branch fossils when they realize we stole one of their precious eyes…"
But even as she said it, the thought twisted deeper inside her — colder, heavier.
The Main Branch…
The people who'd kept her bowed.
Who'd spoken to her like she was furniture.
Who'd smiled while holding a seal that could kill her in a heartbeat.
Who would gladly do it again.
The idea of taking a Byakugan from them wasn't just a strategy.
It was justice.
Reversal.
Proof that she was no longer theirs to command or cage.
But beneath that fire, another thought flickered.
They aren't alone. They have Konoha behind them. They always have.
Even the slightest misstep could turn into a hunt — one they weren't ready for yet.
So she added, quieter, eyes still glowing with Byakugan light,
"…but be careful, Kimimaro. The Main Branch isn't the only enemy tied to those eyes. They have the whole village backing them. If you get caught…"
She trailed off, jaw tightening.
He didn't need her to finish.
He already knew.
But she still said it.
"…just don't make me lose you to them."
Kimimaro paused his writing, the faint scratch of the pen falling silent.
When he looked at her, it wasn't dismissive or scolding, just steady, deliberate, the way he weighed every risk in the world.
"I won't go unless there is an opportunity worth taking," he said. "A massive one. Something that guarantees more than it risks."
He left it at that.
He didn't tell her that he had already calculated when such an opportunity might come based on his past life's knowledge.
Didn't mention the timeline he'd quietly mapped out.
Didn't say that, if the world followed the pattern it should, then the first real opening might arrive in two years already.
"Additionally," he continued seriously, "You shouldn't go anywhere near the Main Branch until your eyes evolve further first. Their command triggers are probably strongest at close range after all. If even one elder got line-of-sight on you, they could activate the seal through every countermeasure we've placed on your forehead. I'm not risking that. And I don't want you anywhere near them or that village yet."
Emi stilled, her expression tightening ever so slightly.
Kimimaro went on, tone even, not cruel, just factual.
"Let me bring the 'samples' first," he said, voice even but edged with finality. "You focus on strengthening your eyes, then. And when they're finally ready, you'll get your revenge without anyone being able to stop you."
He paused, meeting her eyes without a hint of hesitation.
"And what I'm doing now," he said, calm and matter-of-fact, "is still your revenge. Whether it's my hands or yours taking the step… the debt goes against the same ledger."
Before she could fully process that, or let the heat rise to her cheeks, he turned back to the worktable, voice returning to its usual composed tone. "Trust me. I'll bring what we need."
Emi didn't answer right away.
But she understood exactly what he meant.
He wasn't being poetic. He wasn't humoring her.
He was stating a simple truth: in their world, vengeance wasn't about who swung the blade.
It was about intention. About direction.
And theirs were already intertwined more tightly than she liked to admit aloud.
Her Byakugan shifted slightly as the chakra thread she guided wavered, her posture changing from confident precision to a quiet, thoughtful stillness.
Then she let out a slow breath.
"You're right," she admitted quietly. "If I set even one foot near those elders now, they'd flip that seal on without blinking."
Her fingers curled lightly against the metal counter.
"But it still pisses me off that I can't tear it off completely yet."
Kimimaro didn't look up. "You will."
She watched him for a moment longer, her frustration slowly melting into something else, determination, sharper than before.
"…Fine," she said at last. "Go when the time is right. Bring me what I need."
Her voice softened, just barely.
"And I'll make sure those eyes become something the Main Branch never imagined."
She smirked faintly, the fire returning to her eyes.
"But you'd better come back. Otherwise, I'm storming Konoha myself."
Kimimaro allowed himself a small smile at her final words, the faintest nod accompanying it.
Emi's cooperation, no, her eagerness, mattered more than she realized.
Her motivation to dissect every limit of the Byakugan wasn't just convenient; it was essential.
She wasn't simply helping with the research.
She was accelerating it in ways even he couldn't replicate.
And of course, for Kimimaro… this obsession with the Byakugan was never only about Emi.
Helping her achieve true freedom.
Helping her surpass the Main Branch entirely and make them choke on the karma they'd earned.
Helping her rewrite her entire destiny.
Those were all real goals. Important ones.
But they were only the surface.
Beneath them was the true reason.
The reason he cared this much.
For himself.
Because Hyūga and Kaguya were two branches of the same ancient tree.
Hamura's lineage — parallel equations in the architecture of power.
'Tenseigan…'
The word flickered through his mind like a spark catching dry tinder.
His hand tightened around the edge of the table, knuckles whitening for just a moment before he relaxed again.
Emi didn't notice; she was still adjusting the chakra output.
But internally, the thought roared.
The Byakugan wasn't just a tool to refine his Eight Gates or enhance his Yang mastery for perfecting his own Kekkei Genkai.
It was far more than that.
It was a key, a fragment of a forgotten equation that connected directly to the highest tier of bloodline evolution in this world.
And it wasn't even only about the mere possibility of reaching that legendary dojutsu one day.
No, Kimimaro suspected something else.
He speculated deeply that Hyuga might have even more secrets not explored in the original series.
If he could uncover those secrets, too…
Therefore, yes — Emi's revenge mattered.
She stood closer to him than almost anyone, both in practical terms and in emotional ones.
Her dōjutsu, her evolution, her growing strength and freedom — all of it mattered.
But the Byakugan itself…
The Byakugan carried answers.
It opened paths he could not reach through Shikotsumyaku alone.
Paths meant not only for her vengeance, but for his ascent as well.
And Kimimaro intended to claim every last one of them.