The exchange of insights on the Dao, and the realizations after the breakthrough, could only briefly delay the exploration and development of the lake.
Once everything settled, Uchiha Yoru returned to his search beneath the waters.
Fortunately, during his breakthrough, the surge of wind-aspected natural energy had disturbed nearly half the lake's surface. The source they were looking for had to be within that area.
Following the position he had sensed that day, Yoru quickly found it.
A newly formed fissure, buried beneath layers of fallen rock.
Judging by the surrounding terrain, the crack had formed during the landslide.
When the entire opposing mountain collapsed, the impact against the valley floor sent violent shockwaves outward. At a bend in the valley, those waves converged and focused, forcibly tearing open a fissure in the thick bedrock.
Yoru also noticed something else—
Both sides of the valley were composed of sedimentary rock, yet around the fissure there were large amounts of limestone.
That meant the crack ran deep.
Deep enough to reach a different geological layer.
And more importantly—
It was an active spring.
Water rich in natural energy flowed continuously from the fissure, feeding the entire lake.
Yoru collected a small amount of spring water and brought it ashore to study together with Miwa Masayo.
Both of them caught a faint fishy scent.
That meant—
There was abundant life at the source.
"It should connect to an underground river," Yoru concluded. "There are probably quite a few creatures down there. But for now, we can't determine exactly where the natural energy originates."
"Unless we widen the fissure and go down to explore it."
Miwa Masayo immediately shook her head like a rattle drum.
"No. Absolutely not. Yoru, we stop here."
This time, Yoru didn't insist.
He nodded.
Exploring an underground river was far too dangerous.
Even if he could solve the problem of breathing underwater, he couldn't solve getting lost.
And that alone was fatal.
Unlike surface rivers, underground rivers didn't have stable oxygen levels. Even with underwater breathing techniques, safety wasn't guaranteed.
In many underground rivers, water flowing through rock layers would have its oxygen absorbed, creating completely oxygen-deprived zones.
In such areas, aside from specially adapted low-consumption species, even fish would suffocate.
Yoru said, "If we don't explore deeper, there will still be hidden dangers. Creatures from the underground river might enter the lake. That could become a threat to us—and to the ninja cats."
Miwa Masayo frowned.
"We can't block it completely—that's the source of natural energy. But we can narrow it. Leave only small openings. That should stop large creatures from coming through."
"Good idea," Yoru agreed immediately. "We seal most of the fissure, then set up layered traps. One-way traps. Block and capture anything that comes out."
"That way, we not only prevent underground species from invading, but also gather intelligence by studying what we catch."
With the most important issue—the source of natural energy—resolved, and the follow-up plan established, the remaining work could be handed over to the Cat Castle.
Yoru and Miwa Masayo continued to monitor the fissure and the lake while focusing on cultivation and discussion.
Even after exchanging their breakthrough experiences, their communication remained essential.
They were both sages—
But they walked entirely different paths.
Uchiha Yoru's path was an amalgamation—
Fragments of cultivation systems from his past life, Daoist philosophy, the chakra theory of the ninja world, and his own reckless experimentation—
All forced together into a path carved by sheer luck.
After his enlightenment, he had decisively abandoned the traditional cultivation system and developed his own Foundation Establishment method.
But in practice, countless problems remained.
He needed discussion with his dao companion to spark insight.
Miwa Masayo, on the other hand, had spent three years alongside him.
Without realizing it, she had absorbed Daoist philosophical ideas, combined with what she had heard about the Three Great Sage Regions, and formed her own understanding of the Dao.
Because she had already been thinking about the Dao, she was able to sense the disturbance of natural energy during Yoru's breakthrough—
And seize the opportunity to become the first Cat Sage.
Both of them divided natural energy into five aspects.
Both started from fire.
Their starting points were nearly identical.
But their understandings diverged.
Yoru pursued purity of natural energy as his foundation, integrating chakra techniques, walking a path toward balancing all five elements.
A powerful yet composite force.
A restless yet balanced mind.
This allowed him to refine the Uchiha bloodline and draw out its hidden potential, giving rise to incredible abilities.
Miwa Masayo, on the other hand, fused fire-aspected natural energy with fire-release chakra to create fire-based senjutsu chakra.
Perhaps due to that purity, she rejected other attributes entirely.
She walked a path of extremity—
Digging deeper and deeper into fire alone.
As pioneers of their respective paths, neither could rely on traditional sages for reference.
They depended on each other.
Each needed the other's progress to verify their own path.
Discussion—
Argument—
These were their daily routines.
On the morning of the fourth day, while waiting for Maoyou, the two were in the middle of a heated debate about techniques for manipulating fire-aspected natural energy.
Both of them were red-faced from arguing—
When suddenly, they stopped at the same time.
"…A ninja?" Miwa Masayo asked, puzzled.
Yoru nodded, expression turning serious.
"That's right. And not just one. At least four."
His brows furrowed.
"All of them are carrying killing intent. They're not here for anything good."
He spoke calmly, already moving.
"Same as always. I take the front. You stay on the outside and support."
The calico cat nodded, casually igniting a flame—
And vanished into it.
Yoru swept his hand, stirring up a gust of wind that erased all traces of his companion from the ground—
And scattered her scent from the air.
Only after confirming everything was gone did he begin packing his belongings, putting on the appearance of preparing to leave.
A few minutes later—
Three ninja appeared.
From the slopes on both sides of the valley.
And from the southern river.
They quietly formed a loose encirclement.
Yoru reacted immediately.
He dropped his pack and drew his straight sword, taking a guarded stance.
The Sunagakure ninja climbing along the dam was the fastest. He quickly approached and stopped at the edge of shuriken range.
After carefully observing Yoru, he shouted,
"Konoha ninja! What are you doing here?"
According to the rules of ninja encounters, Yoru responded with the firmest tone possible.
"I am a Konoha ninja. This is the Land of Rivers. Sunagakure ninja—you have no right to question my mission."
Another Suna ninja descended from the slope on the left, stopping at throwing distance as well.
He sneered.
"Rules? How naïve. Konoha genin really are simple."
"All rules are just expressions of power."
"There are three of us. You have no right to refuse."
"Otherwise… we'll just take you down and interrogate you properly."
Yoru shifted fully into a combat stance, his voice cold.
"…You can try."
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