Although Arai claimed his duty was to escort Yuji and Sasori safely back to the village, once they returned to the temporary base, he quietly separated the two of them from the larger unit.
Aside from daily perimeter patrols to check for lingering threats, most of his time was spent training Yuji.
Sasori, meanwhile, was left entirely to his own devices.
"You're a medical-nin," Arai said one afternoon after sparring. "Your chakra nature leans toward Yang Release, gentle, restorative, tied to vitality. That makes certain elemental transformations more difficult for you."
They stood on an open stretch of ground within the canyon. The air was dry, the sand shifting underfoot. Arai had just disarmed Yuji in the blink of an eye, his kunai resting lightly at the boy's throat.
Arai wasn't an ordinary jōnin.
As one of the Third Kazekage's personal guards, he ranked among the elite.
No matter what tactics Yuji tried, he couldn't gain the upper hand.
"Most shinobi are born with a dominant chakra nature," Arai continued, lowering his weapon. "They can develop it naturally over time. But that doesn't mean they're limited to just one. By the time someone reaches Jonin level, they usually grasp at least two nature transformations."
He paused.
"However, proficiency varies. Even if someone learns multiple elements, unless it aligns with their innate affinity, or their bloodline, their techniques may lack real power. That's why many shinobi rely heavily on their strongest nature and rarely use the others."
Yuji listened carefully.
"I can't guide you in medical ninjutsu," Arai admitted. "That's not my specialty. But as a medical-nin, if you want to grow stronger, you'll need to supplement it."
He gestured vaguely toward the surrounding terrain.
"Wind, Fire, Lightning, Earth, Water, none of them suit you particularly well. Even if you master one, it likely won't become your primary strength. So your options lie elsewhere."
His smile returned.
"Taijutsu. Ninja tools. Or perhaps puppetry."
He glanced briefly toward Sasori in the distance.
"Medical-nin have exceptional chakra control and endurance. That fits the demands of a puppeteer perfectly. Look at Lady Chiyo. If you chose that path, you'd be more than qualified. Even if you never reached the highest tier, it would significantly raise your combat power."
Yuji had already thought through everything Arai mentioned.
He understood chakra mechanics clearly.
Like Tsunade, some medical-nin relied on overwhelming physical strength and taijutsu. Others, like Chiyo, fused medical precision with puppet techniques.
Both were viable paths.
Arai studied Yuji's expression.
"Judging from your face," he said lightly, "you're not interested in becoming a puppeteer. You're focusing on taijutsu, aren't you?"
Even in their short exchange, Arai had noticed the signs. Yuji's body had been trained thoroughly, disciplined, deliberate conditioning. He wasn't simply building muscle; he was refining something.
Yang Release embodied physical vitality.
"Not exactly," Yuji replied with a sheepish scratch of his head. "I train my body mainly to increase my chakra reserves."
Chakra, after all, was born from the combined energy of body and spirit. Strengthening the body inevitably strengthened chakra output to a degree.
Arai rubbed his chin thoughtfully.
"That explains it. For your age, your chakra capacity, and your mobilization speed are well, above average."
Yuji's training went far beyond simply increasing his strength. Through disciplined breathing and precise chakra control, he gradually strengthened his body from the inside out, improving his stamina, resilience, and overall physical condition.
For shinobi, the chakra network was everything.
The chakra pathways formed the network through which chakra flowed. The Hyuga Clan's Gentle Fist targeted precise chakra points, disrupting that flow and shutting down an opponent's ability to use chakra.
Strengthening those pathways meant smoother, faster chakra control.
"Your taijutsu," Arai asked after a moment, "did you develop that yourself as well?"
During their spar, he had noticed something unusual. Yuji's perception was sharp, almost predictive. His reactions seemed to anticipate movement.
Yuji laughed softly.
"I'm a doctor. When you understand the human body, certain things become instinctive. I can estimate someone's physical condition at a glance, strength, speed, balance. Even in motion, I can read subtle muscle tension and calculate likely movements."
He shrugged.
"But it only works against average opponents. Against someone like you, Arai-sensei, it's useless."
In other words, his so-called "Data Taijutsu" was effective only against low-level opponents.
And the truth was, it wasn't just a doctor's instinct guiding him.
It was his understanding of the world's power system, every pattern, every limitation, every underlying rule he had pieced together in his mind.
A database no one else possessed.
Of course, he couldn't explain that.
He couldn't exactly say he had come from another world where everything here was once nothing more than an animated story.
Arai let out a faint breath.
"As expected," he said quietly, "medical-nin are never simple."
"I'm not that impressive," Yuji replied modestly.
Arai studied him for a moment.
"You already have a clear idea of your combat style and growth direction. In that case, there isn't much left for me to teach you. All I can do is sharpen your taijutsu and give you real combat experience through sparring."
There was something complicated in Arai's gaze.
At Yuji's age, he himself had still been preoccupied with childish things. He hadn't thought so clearly about the future, nor examined himself with such calm precision.
Sometimes, people truly couldn't be compared.
So this was what they called talent.
"Again," Arai said firmly.
"Yes."
Yuji steadied his breathing.
In the next instant, Arai vanished.
Yuji tightened his grip on the scalpel and shifted into a defensive stance.
"Never rely entirely on your eyes," Arai's voice echoed from somewhere unseen. "Your senses can deceive you. In battle, what you rely on most is instinct, refined through experience. Chakra perception is especially important. Energy transfer and release cannot hide."
Yuji's gaze flicked left, then right, searching for movement.
But before he could react, a presence appeared behind him.
Too late.
Smack.
Arai's palm struck the back of Yuji's neck. It wasn't hard, but the meaning was clear.
On a real battlefield, that single opening would have meant death.
"So strong," Yuji muttered, rubbing the spot.
This was the difference.
An Elite Jonin left no visible flaws.
The title of "Elite" existed only within the ranks of Jonin. Among genin and chunin, such distinctions weren't even discussed.
There were Special Jonin, shinobi with exceptional skill in one field but lacking balanced strength.
There were also Lead Jonin, those entrusted with mentoring academy graduates and guiding rookie teams.
Ninja ranks weren't defined by strength alone. The system was layered, nuanced, and sometimes political.
Standards varied from village to village.
The Five Great Shinobi Villages maintained the highest benchmarks, but Konoha's ranking system carried the most prestige.
Not because it was the center of the world, but because many of the shinobi world's rules and institutions had first been formalized there. Others had followed.
"Again," Arai said.
Yuji exhaled slowly.
"Yes."