Kunwu, a Unique Sage Mode

It was a space between reality and illusion, without sky or earth, only boundless warm golden light, as if soaking in the melting sunset.

In the very center of this light, a tiny fox, no bigger than a palm, was curled up with its fluffy tail, fast asleep.

Its fur had a warm, reddish-gold hue, with a few streaks of scarlet markings on its back and tail tip that flickered with its breath, like ancient runes etched on its fur, slowly exhaling and inhaling.

As Natsu's consciousness drew near, the little fox's ears twitched first.

The two pointed ears turned half a circle, then suddenly stood up.

It opened its eyes, revealing a pair of scarlet vertical pupils identical to Natsu's Sharingan, only lacking some of the cold ruthlessness of a killer and possessing more of the innocent and clear-headedness unique to a cub.

The moment it saw Natsu, its tail reacted before its brain—its bushy tail snapped straight up, and then the whole fox, like a furry cannonball, crashed headfirst into Natsu's arms.

"Ooh ooh ooh--" The little fox rubbed its head against Natsu's chin, its four snow-white paws kicking wildly in the air, making a series of sounds from its throat that were like a little animal whining or a cat purring.

It was so small that Natsu could hold its entire body in one hand, yet the affection it evoked was so intense, as if it had been accumulated over several lifetimes.

After all, it was Life-Bound Demon Fox the system had "plucked" from another dimension. In a sense, its soul and Natsu's soul were born from the same source.

Natsu it rub against her for a while before gently pinching the back of its neck and lifting it off her face.

The little fox's four paws were still in a flapping position, and the tip of its tail was bent into a question mark shape in confusion.

"I have something to ask you." Natsu looked into its eyes, her tone softer than when she spoke to people, but still carrying an undeniable seriousness.

The little fox tilted its head, its innocent, scarlet vertical pupils reflecting Natsu's face.

It didn't understand much, but it could sense that its owner wanted to know something from it.

So it closed its eyes, brought its nose close to Natsu's brow, and its wet little nose gently touched his skin.

A warm current flowed from its nose into Natsu's consciousness—fragments of information that the little fox, still in its naive stage and unable to express itself in words, could only convey through this method.

Those fragments slowly pieced together in Natsu's mind.

Sage Mode. Sage Mode unique to the Uchiha Clan.

He originally thought the threshold for this Senjutsu was the Mangekyō Sharingan.

After all, in the Ninja World's understanding, the Mangekyo Sharingan is the pinnacle of Uchiha power, the key to unlocking Susanoo, and the foundation of all Forbidden Technique.

But the fragments sent by the little fox told him—that wasn't right.

The basic requirement for this Senjutsu is not Mangekyo Sharingan at all.

Is it Susanoo?

"Susanoo?" Natsu raised an eyebrow; this answer was somewhat unexpected.

The little fox wagged its tail, as if confirming his question.

The inherited memories in its mind were gradually awakened, and those fragmented images slowly unfolded in Natsu's consciousness.

It turns out that the true nature of Susanoo was never simply Chakra giant.

It is the guardian residing deep within the soul of every Uchiha clan member.

It is not a creation of Dōjutsu, nor an energy mimicry, but some ancient spirit inherited along with the Uchiha bloodline—

Similar to the Guardian Spirit in Rakshasa Street, they are extensions of the soul, embodiments of will, and another self that every Uchiha member carries from birth, sleeping deep within their bloodline.

This also explains why Susanoo can be used before the Mangekyo Sharingan is activated.

Indra summoned Susanoo at the Three Tomoe stage, and so did Natsu himself.

Because the key to unlocking Susanoo is never the Mangekyo Sharingan, but the strength of the soul—and the Uchiha Clan is born with spiritual and soul power far exceeding that of ordinary people, which is why they can awaken their sleeping Guardian Spirit after the Sharingan evolves to a certain level.

The reason this Sage Mode can be achieved is because Susanoo is Origin a being bound to the soul.

It is a bridge connecting the host's soul with the Natural Energy of the outside world.

The ordinary Sage Mode requires the practitioner to absorb Natural Energy and precisely balance it with Chakra within their body; the slightest mistake will result in petrification.

But the Uchiha's Senjutsu is different—it doesn't rely on its own absorption of Natural Energy, but instead introduces Natural Energy into Susanoo, allowing Susanoo.

As Guardian Spirit of the soul, Susanoo is inherently connected to the host's soul. Once it has completed the refining of Natural Energy, this tamed energy will slowly flow into the host's body through the soul connection.

This is not simply about "becoming stronger." It is a complete cleansing from the body to the soul.

The refined Natural Energy will permeate every inch of the cultivator's flesh, every meridian, and every cell, just as Harusame seeps into the earth, day after day.

In this long process of cleansing, the mortal body will gradually shed its impurities and evolve towards a higher level of life form—like turning from carbon into Diamond, the essence is the same, but the structure is completely different.

This process is very slow.

According to the fragments of memory passed down by the little fox, the timeframe ranges from a dozen years to several decades.

But the benefits are equally astonishing. First, the cleansed body and soul will gain a lifespan far exceeding that of ordinary people.

The reason why Hagoromo Ōtsutsuki was able to live for thousands of years was because of the long-term tempering of his Sage Body with Natural Energy.

While the Uchiha clan members may not reach the exaggerated levels of Hagoromo's cultivation of this Senjutsu, extending their lifespan several times over is certainly not a problem.

Secondly, the side effects of the Mangekyo Sharingan will gradually be worn away in this process.

Each time the Mangekyo Sharingan is used, one part of the eye power is depleted; this is a fate that the Uchiha cannot escape.

However, Susanoo's refinement of Natural Energy can nourish the host's soul.

As the soul grows stronger, the depleted power of the eyes can slowly recover;

With physical evolution, the burden of the Mangekyo Sharingan is no longer so heavy. After cultivating to a certain level, the curse of blindness will cease to exist.

What Natsu cared about even more was the last fragment.

When this Senjutsu is cultivated to its peak, the Susanoo of the Uchiha clan will no longer be a half-giant tens of meters tall, but a complete deity thousands of meters high—just like the Majestic Attire: Susanoo Hagoromo Ōtsutsuki in the past, standing tall and overlooking all living beings.

At that time, even the most ordinary Uchiha clan members would be strong enough to rival Hagoromo Ōtsutsuki at his peak.

Seeing that Natsu hadn't spoken for a long time, the little fox nervously tugged at his collar with its paw.

It is still too young, and its inherited memories have not yet fully awakened. The information it can provide is all that it has managed to recall under the stimulation of Natsu's soul aura.