"Learning sensory ninjutsu?"
Hearing Kushina's arrangement, Satoru wasn't surprised in the least.
At the same time, he didn't underestimate sensory ninjutsu just because he already possessed the Byakugan. As Kushina had explained, sensory ninjutsu and the Byakugan were two entirely different systems.
The Byakugan granted a 360-degree field of vision with no blind spots. Once awakened, a Byakugan user could see up to one kilometer away—or even farther, depending on their ability. Every member of the Hyuga Clan had a different range of vision, but most fell within that limit. Even Satoru's own Byakugan could "only" extend about five kilometers.
Moreover, since it required the user to process immense amounts of visual information, maintaining long-distance surveillance demanded extreme concentration.
Limited in range yet terrifyingly precise—that was the Byakugan's defining trait.
But the sensory techniques Kushina spoke of were fundamentally different. Sensory ninjutsu focused on detecting chakra—it couldn't sense things without chakra at all, and its precision was nowhere near that of the Byakugan.
However, in return, its range was far greater. Of course, the exact distance still depended on the user's innate ability; not everyone could perceive across great expanses.
Among sensory-type shinobi, the most exceptional were undoubtedly the Second and Fourth Hokage—both masters of the Flying Thunder God Technique.
Tobirama's sensory prowess was legendary. By merely touching the ground, he could accurately detect an enemy's position, number, and even their relative strength.
The Fourth Hokage, Minato Namikaze, possessed similarly monstrous sensory ability—so much so that even after being revived through Edo Tensei, he could sense the battlefield hundreds of kilometers away.
Sensory ninjutsu excelled in one thing: detecting chakra signatures over vast distances.
For the Flying Thunder God Technique, that ability was indispensable. A user had to sense the location of their marked seal to teleport. The Byakugan's vision wasn't much help in that context—after all, who could calmly scan for seals mid-battle?
Sensory ninjutsu, on the other hand, could pinpoint the marked chakra instantly.
The Byakugan and sensory ninjutsu—two different systems, each with their own strengths.
Even Jiraiya, Minato's mentor, was inferior in that regard. He required a technique like the Detection Barrier to locate enemies, while Minato could do it effortlessly, without even forming a hand seal.
Many who failed to learn the Flying Thunder God Technique had done so simply because they lacked the talent for sensory ninjutsu.
The Uzumaki Clan's secret sensory art was the Mind's Eye of Kagura, a technique with a range spanning ten kilometers or more.
"Sensory ninjutsu is also called target-seeking ninjutsu," Kushina explained.
"In simple terms, it's about perceiving different chakras. The enemy's, your own—it doesn't matter. You need to feel them and distinguish one from another."
"The technique I'm about to teach you is called the Mind's Eye of Kagura."
"You'll merge your chakra with the surrounding air, expanding your perception outward."
"How far you can sense depends entirely on your own ability."
"I'll teach you the seals first—try it out and feel the flow."
Under Kushina's guidance, Satoru began his training in the Mind's Eye of Kagura. He had once assumed the technique was an Uzumaki-exclusive kekkei genkai, but now he realized it was a secret art, not a bloodline limit.
Its casting method was quite unique. Unlike Nagato's Rain Tiger at Will, which infused chakra into raindrops, the Mind's Eye of Kagura merged chakra into the air itself, extending the user's sensory field.
Understanding this, Satoru began to see how Tobirama's ground-touching sensory technique worked as well—the principle was the same, only the medium differed.
Neither technique was inherently superior. The Mind's Eye struggled to detect chakra underground, while Tobirama's had its own blind zones. In terms of precision, both paled in comparison to the Byakugan.
But for mastering the Flying Thunder God Technique… sensory ninjutsu was irreplaceable.
"The range of sensory ninjutsu often correlates with your chakra reserves," Kushina continued.
"The more chakra you have, the farther you can sense."
"I can tell, Satoru—you have an enormous chakra pool. It's not even weaker than mine."
"Calling you a tailless tailed beast wouldn't be an exaggeration. Once you master the Mind's Eye of Kagura, your sensing range might rival my own."
Kushina's voice carried warmth and encouragement. While she guided him to release his chakra into the air, she herself was quietly sensing his energy.
Eyes closed, Satoru formed a single hand seal, focusing his will as his chakra gently diffused into the atmosphere.
He didn't know how long he'd been concentrating when suddenly, within his mind's dark void, a bright light appeared—a luminous sphere radiating immense power and… warmth.
As he focused on it, a wave of wild, feral energy surged from its depths, sending a shiver down his spine. He snapped his eyes open instantly.
At that very moment, deep within Kushina's inner world, something stirred.
The Nine-Tails had awakened.
Its massive body was shackled by golden chains of sealing chakra, nailed against a colossal stone sphere by spikes of light.
Sensing something, the beast's eyes snapped open, and it let out a thunderous roar that shook the entire seal space, the gust of its fury rattling the very fabric of the seal.
Sitting beside Satoru, Kushina frowned slightly as she felt the turbulence within her body. Gently, she pressed a hand to her abdomen.
Golden chains shot out from the void, binding the Nine-Tails' muzzle shut. The roar stopped abruptly, and silence reclaimed the inner space.
Within that silence, the Nine-Tails' eyes burned with blood-red fury—a hatred born not of nature, but of endless imprisonment.
Freedom—so close, yet forever out of reach.
People called the tailed beasts monsters made of chakra and hatred. But how could humans possibly understand? This hatred was not innate—it was forged, day by day, in the darkness of captivity.
When the Sage of Six Paths had divided the Ten-Tails into nine creatures, Kurama had been a small, harmless fox—so innocent that it had cried when they parted.
But now… its chakra seethed with malice strong enough to infect its host.
As Satoru felt that overwhelming emotion through his senses, his eyes flew open, and he withdrew from his inner perception.
He stared blankly at Kushina, eyes wide in shock.
"That was…"
He had realized what that "light" was. It was Kushina's chakra—and from its depths, that oppressive, terrifying presence could only be…
"Oh?"
"You sensed it?" Kushina smiled faintly.
"That's a tailed beast—the Nine-Tails sealed inside me."
"Satoru, when you felt that dreadful presence… were you afraid? Afraid of me, this… monster?"
Her voice was soft, uncertain, almost trembling. As she looked at the young boy beside her, there was a flicker of fragile hope in her eyes.
"Afraid?" Satoru thought for a moment, then nodded slightly.
"A little."
Kushina's gaze dimmed—but only for a heartbeat.
"But what I fear is the tailed beast, not you, Kushina-sensei."
"The Nine-Tails is the Nine-Tails. Kushina-sensei is Kushina-sensei."
"You're not a monster—and I'll never be afraid of you."
Satoru's smile was bright and sincere.
Hearing that, Kushina blinked, then laughed softly. "Yeah… I suppose you're right."
Her voice grew quiet, almost wistful, as she murmured to herself—
"I guess… my own child in the future won't be afraid of his mother either, huh…"
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