For four consecutive days, Iruka spent every moment he wasn’t resting in the library.
The reason was simple: he needed a deeper understanding of chakra.
The library contained all kinds of books discussing chakra, from its applications to various theories and insights.
Such books were naturally of little use to ordinary shinobi.
After all, they had been exposed to chakra since childhood, learning and practicing alongside one another until they could put that knowledge into practical use.
How could they possibly be unfamiliar with it?
But Iruka was different.
Although he could use chakra, unlike other shinobi, who used it to perform all manner of ninjutsu, Iruka’s chakra had merely served as a substitute for the psychic force of his previous world—a supernatural source of energy that allowed his Spirit Domain to connect with reality.
He knew virtually nothing about ninjutsu.
After all, ninjutsu and esper abilities were entirely different systems of power.
Their only real similarity was that both required supernatural energy.
Beyond that, they were fundamentally different.
How could Iruka have understood ninjutsu from the very beginning?
Originally, Iruka had believed that by using his abilities frequently, he could take advantage of the body’s natural adaptation to external stimuli.
By rapidly depleting his chakra and allowing it to recover over and over again, he hoped to stimulate an increase in his chakra reserves.
However, after his battle with Itachi, he discovered that this approach didn’t work.
Later, he discovered that the colorless chakra of unknown origin repelled his blue chakra.
For the time being, he had no choice but to abandon the idea.
After four days of practically living in the library and absorbing every piece of knowledge about chakra he could find, Iruka had not only gained a nearly comprehensive understanding of conventional chakra theory, but had also reached a conclusion that was extremely useful to him.
Blue chakra could be strengthened through the use of ninjutsu.
That’s right.
The problem that had been troubling Iruka—the fact that his chakra reserves couldn’t increase—had finally been solved.
His original theory had been correct: by taking advantage of the body’s natural adaptability and repeatedly cycling through chakra depletion and recovery, it was possible to increase one’s chakra reserves.
The reason his chakra reserves hadn’t increased at all after fighting Itachi was because he hadn’t used ninjutsu.
He had used his esper abilities instead.
In other words, only by using ninjutsu could he strengthen his blue chakra.
The other problem had been resolved as well.
The colorless chakra interfered with the circulation of his blue chakra when he used his esper abilities, but it seemed that as long as the blue chakra wasn’t being used to activate those abilities, it wouldn’t come into contact with the colorless chakra at all.
As long as he used it solely for ninjutsu, there was no problem.
Iruka had reached this conclusion after learning the basic Transformation Technique.
However, the technique consumed far too little chakra for his findings to be considered completely reliable.
He would need to test his theory with more advanced ninjutsu.
“Haaah…
Time to head home.”
Iruka closed the thick book in front of him and stretched for the first time in what felt like ages.
His stiff body cracked and popped as he stretched—a clear indication of just how long he had been sitting there.
After returning the book to its shelf, Iruka finally left the library.
The sky had been clear when he arrived.
By the time he left, the moon was high and the stars were sparse.
Walking alone through the deserted streets, Iruka’s expression remained eerily calm, without the slightest ripple.
When he reached an empty alleyway, he suddenly stopped, as though waiting for someone.
Before long, distinct footsteps slowly sounded behind him.
“Oh?
You noticed me?
I see…
With perception like that, it’s no wonder you were able to detect Zetsu’s presence.”
The speaker was a man wearing an orange mask patterned with black markings.
His entire body was concealed beneath a loose, high-collared cloak, while long black hair swayed in the night breeze.
Everything about him exuded an unsettling, mysterious aura.
Iruka slowly raised a hand.
In an instant, his chakra surged to its limit.
In less than two seconds, he had analyzed every force field throughout the area and was ready to use Vector Control to completely encompass the surrounding space.
Once he had finished preparing, Iruka asked in a low voice,
“Who are you?
What do you want with me?”
This was completely different from his encounter with the ANBU squad led by Itachi.
Although there was only one opponent before him, Iruka instinctively sensed an extreme danger emanating from the masked man—one even greater than what he had felt when facing Itachi.
Against an enemy of this caliber, psychological tactics were meaningless.
He could only respond in the most direct way possible.
“A guide who will correct this mistaken world and lead it toward its proper future.
As for why I’ve come looking for you…”
The masked man raised one hand as well, his black-gloved palm facing Iruka.
“Because you have become an obstacle to this world’s rightful course.”
Crack!
Crack!
Crack!
The ground around the masked man suddenly writhed.
In the next instant, four massive earthen spikes erupted from the ground, piercing straight through him.
The battle appeared to be over in an instant.
Yet Iruka showed no sign of relief.
On the contrary, his expression grew even more solemn.
The masked man’s body had clearly been pierced, yet not a single drop of blood was spilled.
Nor had his body been lifted by the spikes.
There was no sensation of having struck flesh at all.
It was as though the earthen spikes had simply passed through his body.
As if confirming Iruka’s suspicion, the masked man’s hand twitched slightly.
Iruka’s eyes widened in alarm.
He immediately manipulated the surrounding force fields, lifting chunks of rock into the air.
Less than two seconds later, the rocks suspended by antigravity suddenly shattered, and a sharp whistling sound tore through the air as something came hurtling toward him.
Fortunately, the rocks had bought him enough time to react.
Iruka immediately used his ability to reduce the gravity acting on himself to the absolute minimum.
With a powerful push from his feet, his body shot upward into the air, eventually coming to a stop above the alley.
Once he stabilized himself, Iruka quickly turned to look down at the masked man.
Never take your eyes off your opponent during a battle.
That was basic common sense.
But when he looked down, the place where the masked man had been standing was completely empty.
Only a faint, spiraling distortion remained behind.
“It’s over.”
A cold voice suddenly sounded behind him.
Iruka’s heart skipped a beat.
It was already too late to turn around.
Without hesitation, chakra surged through his body as he activated his ability once more.
“Gravity Field!”
The gravity acting on Iruka instantly increased tenfold.
His body plummeted straight toward the ground like a cannonball, and his flesh-and-blood body slammed violently into the earth, sending dust billowing into the air.
“I see…
So his ability isn’t to control rock, but to manipulate objectively existing forces…”
The masked man hovered calmly in the air as he withdrew a black rod that had extended from his sleeve.
A spiraling distortion then appeared around him, and he vanished once again.
A moment later, he reappeared on the ground.
As the dust gradually settled, Iruka’s battered figure was revealed.
Iruka was in terrible condition.
His body was covered in dust, and his green Konoha flak jacket had been completely ruined.
The exposed skin beneath it was covered in cuts and abrasions, while his forehead had been scraped open, blood continuously running down his face.
His most serious injury, however, came from the tenfold gravity and the impact of hitting the ground.
The force had displaced his internal organs.
He now had to devote a portion of his chakra to using his ability to stabilize them in place.
Otherwise, even if he somehow managed to drive the masked man away, internal bleeding would kill him afterward.
Earlier, while he had been in the air, Iruka had never expected his opponent to suddenly appear directly behind him.
Caught off guard, his only option had been to increase the gravity acting on himself and create distance as quickly as possible.
Although he could manipulate the force fields around his body to move freely through the air, his current chakra reserves and chakra control were too limited.
When it came to a naturally occurring force like gravity, he could only control its positive and negative direction.
To move sideways, he would have to either manipulate the wind or generate a force field from nothing.
Either option could easily get him killed before he had time to evade the masked man’s attack.
The force of the wind was far weaker than the gravity constantly acting on him, and it was also more complicated to manipulate.
Increasing its strength required chakra, while changing its direction required analyzing its original flow.
Inevitably, that took time.
Even with Iruka’s analytical ability, he needed two seconds.
The masked man would kill him in one.
Generating a force field from scratch was no different.
The preparation time would certainly exceed one second.
If this had been his previous body in his former world, even suddenly increasing the gravity acting on himself a hundredfold wouldn’t have harmed him in the slightest.
With his precise control, he could have handled it perfectly.
But now, he was merely an ordinary chūnin with limited chakra reserves.
He had never systematically trained in the precise control of a fixed amount of chakra, so he couldn’t manipulate it with complete freedom.
Getting injured was unavoidable.
“Cough!
Cough!”
Iruka suddenly began coughing violently.
A moment later, a metallic taste filled his throat.
Pfft!
Iruka spat out a mouthful of blood.
It was stagnant blood that had accumulated inside his body.
After coughing it up, his complexion finally improved slightly.
Only then did he raise his eyes and stare solemnly at the masked man in the distance.
His injuries were severe, but that didn’t mean he had lost his ability to fight.
As someone who possessed the traits of both a shinobi and an esper, as long as he still had chakra, he could still use his abilities.
And as long as he could use his abilities—
He still had the strength to fight!