Of course, Rokuro never mistook the Substitution Jutsu for true space–time ninjutsu, but even so, it was still one of the most ingenious techniques in the shinobi world.
Whether used in low-level skirmishes or among the highest ranks, it always had its place.
Even during the Battle of the Gods, Madara Uchiha's Limbo: Border Jail carried elements of the Substitution Jutsu. That alone showed just how practical the technique was.
"Aside from the Sharingan and Byakugan, the most effective way to counter Substitution Jutsu is through chakra sensing."
In the shinobi world, there were specialists called sensory-type ninja. But as far as Rokuro was concerned, even ordinary ninja had some level of chakra perception—it was just that their range and precision couldn't compare to a true sensory type.
Although Rokuro himself wasn't one, as a master of sealing techniques, he possessed exceptional chakra control—and that alone granted him above-average sensing ability. In close combat, at least, he could clearly feel the fluctuations in an enemy's chakra.
It was that same ability that allowed him to detect the Vacuum Shuriken in the nick of time during his fight with Orochimaru.
"Still, my sensing ability falters when I'm focused on ninjutsu. During intense battles, my awareness splits, and chakra perception drops drastically. Especially when fighting someone like Orochimaru—a true master of ninjutsu—it's easy to overlook details. Looks like I'll need to craft a sensory-type ninja tool."
Rokuro had always taken sensory techniques seriously.
When he broke into Hiruzen Sarutobi's house during the Nine-Tails' Night to steal the Scroll of Seals, the very first jutsu he learned was a sensory technique—proof enough of how highly he valued it.
"As a Uchiha—even a half-blood one—I'll probably awaken the Sharingan eventually. Maybe not the Mangekyō, but at least a pair of three-tomoe eyes shouldn't be out of reach. The Sharingan does have great sensory potential, but compared to dedicated sensory techniques, it's still a little lacking."
To Rokuro, the greatest strengths of the three-tomoe Sharingan lay in its dynamic vision and its resistance to genjutsu.
In terms of perception, it simply couldn't match the Byakugan.
If he had been born a Hyūga, he wouldn't even need to learn sensory jutsu.
Even a branch member marked with the Caged Bird Seal could surpass most sensory specialists with their Byakugan alone.
But as an Uchiha, he didn't have that advantage—so learning a sensory technique was absolutely necessary.
"Even the Mangekyō, even the Rinnegan, can't compete with the Byakugan when it comes to raw perception. A sensory-type ninja tool would be useful even in a battle among gods."
The reason Rokuro valued perception so highly was because ninja combat itself revolved around deception and misdirection.
Just look at the three basic jutsu every academy student learned—Clone, Substitution, Transformation.
All of them existed to deceive the enemy's eyes.
Countless advanced techniques were merely extensions of that same principle—Shadow Clones, Shisui's Instant Movement Clone, Earth Release: Decapitation Technique… all designed to catch opponents off guard.
A skilled sensory ninja could easily pierce through such illusions.
Of course, seeing through them didn't guarantee victory—you still needed the strength to act on it.
"During today's fight, I nearly got caught twice. The first was when that giant snake swallowed me. If I'd realized earlier that it was just an earth clone, I wouldn't have fallen for it."
"The second was the Vacuum Shuriken—if I hadn't reacted in time, my Lightning Armor would've been shredded, and I'd be missing a few pieces of myself right now."
"If I'd had a sensory tool back then, I could've avoided both."
After reviewing the battle in his mind, Rokuro pinpointed his greatest current weakness.
Combat experience could only be gained through actual fighting—no amount of theory would make up for that.
"Come to think of it, the village should've assigned me a team and a jōnin instructor by now. Doesn't matter who I get, as long as it's not that filial fool…"
After a night's rest, a messenger arrived the next morning with a summons.
Rokuro was to report to the Academy—his jōnin instructor had been chosen.
When he arrived, however, expecting to meet his new teammates, he found the classroom empty—no one there but himself.
He waited for a while, assuming the others were late.
But soon, a cold, serpentine aura drifted in from the hallway.
"No way… you've gotta be kidding me…"
Under Rokuro's uneasy gaze, Orochimaru himself walked in, calm and smiling faintly.
"Good morning, Rokuro. From today onward, I'll be your instructor."
Rokuro had already suspected it—but hearing it out loud still made him want to swear out loud.
"Orochimaru really knows how to pick his students. To think one of the Legendary Sannin would take me under his wing… what an honor."
"Heh… the honor's mine as well," Orochimaru replied smoothly. "Come. Let's talk somewhere more private."
Meanwhile, in the Hokage's office, Hiruzen Sarutobi sat quietly, reading through Rokuro's file when the door creaked open and Shimura Danzō stepped inside.
"Hiruzen, I hear Orochimaru's taken an Uchiha as his disciple? What's that fool thinking? Has he forgotten the Uchiha are still the prime suspects behind the Nine-Tails incident?"
Hiruzen set the folder aside and took a slow puff from his pipe.
"Uchiha Rokuro is only six years old, Danzō. There's no way a child like that could've released the Nine-Tails. Don't overreact."
"Hmph. You should still be cautious. Orochimaru's getting more reckless by the day."
The two men had once been allies.
Their methods were equally ruthless, but their goals were not.
Orochimaru pursued knowledge—science and truth.
Danzō pursued power.
For a time, they could cooperate. But the divide between them grew too wide, and their eventual fallout came with the Wood Release experiment—after Yamato's early exposure, thanks to Rokuro's interference.
From then on, their relationship was completely severed.
"Forget Orochimaru for now," Hiruzen said. "What's the situation with the Uchiha?"
Danzō gave a dry chuckle.
"My men have them surrounded. Every move they make in their new compound is under surveillance. But Hiruzen, those ungrateful wolves will cause trouble sooner or later. Wouldn't it be better to end it quickly—cut the weed before it grows?"
Hiruzen was silent for a long time before shaking his head.
"The time isn't right. Konoha can't afford internal conflict right now. We'll wait."
Danzō's lips twisted in a cold sneer.
"Just don't regret it later. Killing danger in the cradle is the best way to protect the village."
"I don't need you to remind me," Hiruzen said sharply. "I'm the Hokage. I know what must be done."
With a snort, Danzō turned and left.
While the two old men argued behind closed doors, Rokuro was already standing in one of Orochimaru's underground laboratories.
All around him were jars of preserved specimens—mostly animals, thankfully, but the sight was still unsettling.
Orochimaru turned, holding a large scroll in his hand.
"Rokuro, take this back and study it."
Rokuro unrolled it—and his eyes widened in surprise.