Early morning.
Naruto's internal biological clock rang like an alarm, and he rose from bed automatically.
After washing up and finishing a quick breakfast, Naruto was about to pack his schoolbag for the Academy when he suddenly froze. A strange feeling washed over him—something indefinable but powerful. He set down the bag and walked to the bedroom to wake Nine-Tails.
"What now? I haven't gotten enough sleep yet." Nine-Tails rubbed his sleepy eyes, clearly annoyed at being disturbed. His irritation was compounded by the fact that Naruto hadn't come home for dinner a few days ago. The fox was still holding a grudge about that.
"We're going to the back mountain," Naruto said simply.
"Huh? Don't you have to go to school?" Nine-Tails asked with curiosity, his annoyance momentarily forgotten.
"Not today." Naruto's voice held quiet certainty. When he'd been packing his schoolbag just moments ago, that strange feeling had struck him—a premonition that today might be different. Today, something important might happen.
He'd been practicing the Iron Body Technique and had reached the final position before achieving true mastery—before officially entering the technique.
Today might be the day of breakthrough. An opportunity for enlightenment.
After Nine-Tails finished washing up with surprising speed, Naruto scooped him up and headed to the back mountain.
When they arrived at the training ground, Naruto found a large, flat boulder and climbed onto it. But he didn't immediately begin practicing the Iron Body forms. Instead, he simply stood there quietly with his eyes closed, feeling everything around him.
The sound of wind rustling through leaves...
The distant calls of birds...
The gentle whisper of grass swaying...
All the natural sounds of the world.
He was searching for a feeling—that elusive sensation of perfect harmony, of everything clicking into place. The feeling of breaking through to the next level.
Half an hour passed in stillness.
Then Naruto's eyes opened, and he began to move.
Starting position...
Naruto shifted slowly, deliberately, with a completely relaxed expression on his face. But from within his body came the powerful sound of ki and blood rushing through his veins like a river in flood. His movements weren't hurried. Each gesture flowed into the next with perfect smoothness, as if everything around him—the air, the trees, the very earth—was in complete harmony with his rhythm.
The heart of heaven is my heart, he thought, losing himself in the flow.
Time became strange. It passed very slowly, each second stretching out endlessly. Yet it also seemed to fly by in an instant, minutes vanishing like smoke.
At the Academy, the day progressed normally. When school let out, Sasuke noticed immediately that Naruto hadn't shown up at all. Concerned and curious, he made his way to the back mountain after classes ended.
There, he found Naruto standing on top of a large stone. His body moved through strange postures with glacial slowness, each position flowing seamlessly into the next. Sasuke couldn't identify what exactly Naruto was doing.
But the strange thing was that Naruto's gestures seemed to contain some profound meaning—something deep and unfathomable that Sasuke couldn't quite grasp. The movements held a mysterious quality that made them mesmerizing to watch.
Unable to understand but not wanting to interrupt, Sasuke walked to a spot nearby and began practicing his Fire Style jutsu against the broken trees that littered the training ground.
An hour later, Naruto's body began to undergo a dramatic transformation.
First, his height increased significantly, his frame expanding upward. His skin flushed a deep, vibrant red—the color of heated metal fresh from the forge. When Naruto completed the final position in the sequence, his height had stabilized at exactly two meters tall.
"Hah!" Naruto released a long, powerful breath. The rosy flush gradually faded from his skin, returning to its normal wheat-colored tone. He stood there for a moment, examining the changes in his body with intense focus and wonder.
Suddenly, a voice echoed through his mind—the system's voice, clear and congratulatory.
[Congratulations, Naruto! You have officially entered the Iron Body Technique. Your skin is now like copper, your bones like iron. Blades cannot pierce your flesh. You have truly embarked on the path of Ultimate Taijutsu.]
"So this is what it means to officially begin the path?" Naruto murmured to himself, a grin spreading across his face.
Now that he'd achieved entry into the Iron Body Technique, it was time to test whether the legendary effect was real—whether blades truly couldn't harm his body.
With this thought in mind, Naruto called out to Sasuke, who was still practicing his Fire Style. "Sasuke! Come stab me!"
Sasuke, lost in concentration on his technique, didn't hear clearly. He thought Naruto must be joking. Looking over with confusion, he asked, "What did you say?"
Then Sasuke's eyes widened in bewilderment. He noticed that Naruto had grown taller again—now standing at an imposing two meters. Meanwhile, Sasuke himself was only 1.3 meters tall. The difference was staggering.
"Sasuke, come on!" Naruto repeated with more emphasis. "Take out your kunai and stab me a few times. Go ahead!"
Sasuke's face darkened immediately. Stab you with kunai? Are you insane? Are you having some kind of crisis?
Seeing Sasuke's continued hesitation, Naruto changed his approach. "Sasuke, let's have a real battle between ninjas."
A real ninja battle meant going all out—fighting with the genuine intent to defeat your opponent. In such a battle, any trump cards or hidden techniques would inevitably be revealed, one by one.
Since Naruto had formally invited him to fight, Sasuke naturally wouldn't refuse. He nodded, adjusted his chakra flow to optimal levels, then gave Naruto another nod to signal his readiness.
The moment both boys were prepared, Naruto stepped forward. His movement brought forth the whistling sound of wind rushing past his body.
On his side, Sasuke's fingers flipped through his kunai pouch with practiced precision. Several shuriken appeared in his hand. He threw them with considerable force, and the projectiles—glinting with cold, sharp light—shot through the air directly toward Naruto's chest.
Facing the incoming barrage, Naruto's face showed nothing but confidence. He stretched out his hands—as large as fans—and reached out to intercept the shuriken flying toward him.
Ding, ding, ding!
A series of metallic sounds rang out, clear as bells. The shuriken were swept aside by Naruto's large hands, deflected harmlessly away. Not a single one managed to strike him. After defending against the attack, Naruto examined his hands carefully. Sure enough, except for some barely visible white marks on his skin, they were completely uninjured.
Sasuke, who was already preparing his second round of throws, felt his pupils contract sharply in surprise. He caught the shuriken with his bare hands and wasn't injured at all? Ninjas were taught to catch or deflect thrown weapons using skill and technique, redirecting the force.
But Naruto had simply grabbed them head-on—pure, straightforward defense.
Surprise aside, Sasuke's second volley didn't slow down. In an instant, ten more shuriken flew through the air toward Naruto.
Having gained a clear understanding of his new capabilities, Naruto now knew with certainty that he could withstand cold weapons at the entry level of the Iron Body Technique. Therefore, he didn't bother trying to sweep these projectiles away with his hands like in the first round. Instead, he simply let go of his defensive posture completely, allowing the shuriken to strike his body directly.
Ding, ding, ding!
Ten crisp, clear ringing sounds echoed through the clearing.
It had to be said—Sasuke's throwing technique was extremely sophisticated and precise. He'd clearly practiced extensively. The ten shuriken covered Naruto's entire body: one aimed at his face, one at his chest, and two each for his limbs.
Each weapon struck true... and bounced off harmlessly.
Naruto felt pure joy surge through him. His Iron Body Technique had truly reached entry level—blades could not pierce his flesh! Unable to contain his elation, he burst out laughing, the sound echoing across the training ground.
Seeing Naruto suddenly stop and laugh with such genuine happiness, Sasuke ceased his attacks as well. He walked up to Naruto, his face filled with intense curiosity about exactly what kind of technique Naruto had been practicing.
Naruto noticed Sasuke's obvious curiosity and smiled. "Sasuke, you probably have a lot of questions, don't you? I told you before—I'm practicing Ultimate Taijutsu, the way of the Iron Body."
"Iron Body..." Sasuke processed this, then looked up at Naruto's towering form. "So you're tempering your skin until it becomes like a block of iron? Hard and impenetrable?"
"No, not quite. You'll understand better if you touch my skin for yourself." Naruto extended one arm, gesturing for Sasuke to examine the texture.
Sasuke reached out and pinched Naruto's arm experimentally. The skin's texture felt completely normal—exactly like his own, not hardened or different in any obvious way. Yet somehow, this normal-feeling skin had caught shuriken without sustaining any damage at all.
This is the true power of Naruto's Ultimate Taijutsu, Sasuke realized with growing amazement.
Naruto deactivated his technique, his body shrinking back down to his normal height of just over 1.6 meters. Maintaining the transformed state while talking to Sasuke had been tiring—he'd had to constantly look down at such a steep angle. If he kept his head tilted down for too long, he'd inevitably develop neck and spine problems.
Seeing Naruto return to his normal form, Sasuke breathed a quiet sigh of relief. Naruto's transformed state had been incredibly oppressive—the sheer physical presence had been overwhelming. Communicating while constantly looking up had been exhausting for Sasuke as well.
Three hundred meters away, hidden within the branches of a large tree, the ANBU operatives assigned to monitor Naruto showed no unusual reactions on their masked faces.
To them, it appeared that Naruto's body was perfectly normal. The sight of shuriken bouncing off his flesh hadn't registered at all—they simply hadn't seen it happen.
This wasn't because they were inattentive. The system had been using concealment techniques on these two from the very beginning. Even though they followed Naruto constantly, they would never notice anything strange about his abilities or training.
The dimensional difference between the system's power and theirs was simply too vast.
If they had actually noticed Naruto's current physical condition—if they'd witnessed what his body could do—they would have reported to the Third Hokage immediately, and everything would have changed.
But they remained blissfully unaware, watching a completely ordinary training session between two young Academy students.