It wasn't that Kimimaro was outright stronger than her, or that he would necessarily fare better against some third-party neutral shinobi.
The truth was simpler: his resistance to genjutsu happened to counter her style almost perfectly.
From his current perspective, only the Mangekyō Sharingan's special abilities could hope to bind him fully.
Even then, he had already begun laying the groundwork for contingencies.
In his mind, fuinjutsu was the natural answer, an inscribed head-seal that could quietly absorb and neutralize any Yin-based intrusion before it reached his core brain chakra point.
He even envisioned building it with a massive chakra "battery," something that could keep working under constant assault.
That project would have to rest in the near term, given his other priorities, but he was certain it would be complete and ready by the time the true storm of the world, the "plot", finally began in a few years.
He already talked with Ashina regarding the viability of it, and the man was once again amazed at his unconventional ideas.
For now, they all hovered around high-jōnin level, including Kimimaro himself, if he set aside his constant caution over preserving his health.
Emi remained the outlier, still only at high-chūnin, for reasons that were obvious enough.
Yet even that wouldn't last.
If the experiments tailored specifically for her bore fruit, her rise could come suddenly, almost overnight, in the years ahead.
Kimimaro's short assessment of Akane was clear.
She stood out as one of the rare shinobi born with twin affinities: fire, as expected from nearly every Uchiha, but also lightning, a unique gift inherited from her father, who had been one of the clan's few secondary lightning specialists.
That alone gave her unusual potential.
He couldn't help but wonder if she might follow Emi's example one day, if it proved successful, fusing her elements into something rarer, some advanced release unique to her.
But that was a matter for the future.
For now, her true strength was obvious: the fully stabilized three-tomoe Sharingan spinning in her eyes, sharpening her perception and gifts with every passing day.
Her father had already passed down a repertoire of fire and lightning techniques, and Kimimaro had no doubt she would master them in due time.
In fact, with a three tomoe, she had a near-perfect, advanced copying, and could automatically soon pick literally all of her father's techniques.
What lingered in his mind, though, was the pity of it, that she hadn't awakened the Mangekyō at that time as well, as he hypothesized she could due to her genetic luck.
A rare treasure among rarities, and beyond that, a power that tilted the scales of history.
Kimimaro knew how impossible it was to simply will such an evolution into being.
Trauma, grief, unbearable loss, that was the soil in which the Mangekyō bloomed.
It couldn't be tricked with simple genjutsu, even a complex group genjutsu, because if it could, the Uchiha themselves would have spawned Mangekyō users endlessly, until their entire clan were monsters - and conquer the world, creating some eternal 'Uchiha Kingdom'.
But what if there was another way?
He entertained the thought like a forbidden puzzle.
If the key was not the illusion of loss, but the experience of it, then perhaps Yin and Yang together could sculpt that reality.
An experiment, an elaborate ritual, something that could trick the body and soul into believing the trauma was real, forcing the eye to break its own limits.
The result would be hatred turned into light.
Power wrenched out of despair.
And if it worked?
Later, instead of resenting him, she might very well thank him.
Gratitude would replace bitterness.
Because for Akane Uchiha, what she desired above all else was not comfort, not peace, but power.
Meanwhile, as the spar finally died down, Kimimaro let his drill-lance fade back into bone and folded his arms, eyes steady on her.
"Your prediction ability is simply unmatched," he admitted plainly.
"Every move I made, you picked the right answer, whether it was cutting off my counters or slipping into the openings I left. But…"
His gaze swept over her, deliberately sharp, "…your body is still too underdeveloped and untrained to capitalize on it properly, compared even to my four-year-younger one. Tell me honestly, did you even train at all before?"
Akane's cheeks colored instantly, Sharingan dimming as she looked aside.
"Don't take it the wrong way," she muttered, crossing her arms over her chest. "I was constantly on trips with my father, riding caravans, handling clan business. That's why my physical condition… wasn't exactly ideal."
Kimimaro grinned. "Then from now on, you'll join me in my training."
Her blush deepened, remembering all too vividly his brutal morning routines, six hours straight of endless physical grind, sweat pouring off him until his frame looked carved from steel. Her voice stammered, rare cracks in her proud composure.
"N-no way. You just want to watch me in that state too… to take advantage."
Kimimaro sighed, as if she were the one being ridiculous.
"Then I'll give you my protocols and experience to follow instead. But either way, you'll train. Otherwise, your eyes won't save you when your body can't keep up."
And then, with that same unnervingly calm tone, he surprisingly added, "Besides, with those lumps of flesh, you'd just get in the way. I'd rather stay disciplined."
Silence hit like a slap.
Her lips parted, her face flushing as red as her clan's fan as the meaning fully sank in.
"Lumps of… flesh?" She repeated, the words dragging out of her like they'd just pierced straight through her pride.
Her composure shattered at once, fury and embarrassment spilling through the cracks. "You—you insolent—!"
Then, impossibly, she pouted. Actually pouted. Lost for words, flustered beyond recovery, her proud Uchiha dignity collapsing into one small, indignant girl who suddenly wanted to throttle him far more than stab him.
Kimimaro, meanwhile, had already looked away, utterly unconcerned, as if she'd vanished from his awareness the moment he finished speaking.
Inside the pendant, Ashina had to restrain himself from groaning aloud.
A century plus of experience, and yet somehow fate had tied him to this one, this strange, calm boy who showed no interest beyond climbing to power, yet managed to accumulate more stunning, volatile girls around him than anyone he'd ever known - "accidentally".
All unique, all bound to him in their own peculiar ways. Ashina muttered inwardly, "What sort of disciple am I saddled with? A tyrant-in-training… or some accidental magnet for chaos?"