After reaching these conclusions, Hoshiyomi finally felt relieved. He went straight to Kuugetsu and told her about his research findings.
Although Kuugetsu had no ambition to dominate the shinobi world, she couldn't help feeling excited when she heard that her Mangekyō still had room for advancement.
There wasn't much to say about the process of evolving Kuugetsu's Mangekyō into the Eternal Mangekyō. It was no different from Shin's experiment: simply infusing special Yin-Release chakra until the quantity triggered a qualitative transformation.
After Hoshiyomi infused nearly two-thirds of his Yin-Release chakra into her, Kuugetsu's Mangekyō naturally evolved into the Eternal Mangekyō Sharingan.
As for the Rinnegan above that—Hoshiyomi was powerless. Although Hashirama cells could supply Asura's chakra, Hoshiyomi had no way to create Indra's chakra; thus, an artificial Rinnegan was impossible.
With Kuugetsu's Mangekyō upgraded to the Eternal Mangekyō, Hoshiyomi no longer needed to worry about her going blind.
With his biggest concern resolved, Hoshiyomi's thoughts began to wander.
He had fought Uchiha Madara before—and Madara's Susanoo had left a deep impression on him. When Kuugetsu still had an ordinary Mangekyō, Hoshiyomi strictly forbade her from using Susanoo.
But now that her Mangekyō had evolved into the Eternal Mangekyō, Hoshiyomi naturally wanted to see her Susanoo.
Feeling her own evolution into the Eternal Mangekyō, Kuugetsu also felt tempted by Hoshiyomi's suggestion.
She had actually been able to use Susanoo long ago. During the fight against Fugaku's father and the Nine-Tails, she had even considered using it as a last resort. But that time, she got caught by Izanagi, so the chance slipped away.
After receiving Hashirama cells she could have used it, but Hoshiyomi kept telling her to wait until she reached the Eternal Mangekyō so she could use the Perfect Form. And that delay stretched all the way to today.
Now that her eyes had finally evolved, Kuugetsu was more than curious about her Susanoo.
After the two finalized their decision, they quietly left Konoha and found a desolate mountain within the Land of Fire as their testing site.
Before letting Kuugetsu use her Susanoo, Hoshiyomi deliberately activated Sage Mode to scan the surroundings. After confirming there were no White Zetsu nearby, he nodded to her.
At this point, even Kuugetsu had grown impatient. Seeing Hoshiyomi's signal, she wasted no time and activated her Eternal Mangekyō.
The eerie Mangekyō pattern appeared in her eyes, and guided by her willpower, a terrifying energy erupted instantly.
A deep violet-red chakra flame burst into life around Kuugetsu. As the flames grew stronger, they condensed into a skeletal frame that looked almost solid.
With Kuugetsu continuously pouring in ocular power, the massive skeletal structure began to develop muscle textures, and eventually a chakra robe that resembled clothing.
In the hands of Kuugetsu's violet-red Susanoo, a weapon slowly materialized—not Madara's great sword nor Sasuke's bow, but a long, elegant naginata.
Kuugetsu seemed intrigued by the weapon. She paused her chakra flow and instead manipulated her Susanoo to swing the naginata experimentally.
Although she had never used a naginata before, controlling a giant weapon like this required no skill—just overwhelming force. Simply swing it with full power and be done.
After twirling the naginata in both hands, Susanoo brought it down in a massive strike. The momentum of the blow was astonishing—where it passed, it carved a violet-red arc through the air.
When the naginata struck the ground, it sliced out a deep trench, and within the trench, violet-red chakra flames continued to burn fiercely.
Those flames were not on the same level as Amaterasu, but in Hoshiyomi's eyes they were comparable to the Two-Tails' chakra flames—definitely not something ordinary Water Release techniques could extinguish easily.
After swinging the naginata twice to her satisfaction, Kuugetsu withdrew her attention and continued injecting ocular power into her Susanoo.
At this stage, her ocular power was nearly inexhaustible, and since Kuugetsu herself was already a veteran Kage-level powerhouse, she didn't have to worry about exhausting her chakra either.
With the continued influx of ocular power, Susanoo underwent further changes. Heavy armor formed over its frame, followed by the emergence of legs. Kuugetsu could now stand at the center of Susanoo's brow, controlling its movements freely.
This level of Susanoo was just right for Kuugetsu—something she could still control with relative ease. She could summon the Perfect Susanoo above this stage, but only for a short time.
However, today's purpose was to see the full form, so she didn't worry about that.
Gritting her teeth, Kuugetsu poured all remaining chakra into Susanoo. Supported by her chakra and ocular power, the already massive Susanoo grew even larger.
But this time, Kuugetsu's Susanoo didn't transform the same way Madara's or Kakashi's did.
Her Susanoo did form armor, but it wasn't as heavy or massive as theirs. Instead, the wings behind it underwent dramatic changes.
Kuugetsu's Perfect Susanoo looked slightly smaller than Madara's, but its wings were far more refined. Every feather was clearly defined, looking as though a single flap could unleash a storm of razor-sharp blades.
Unfortunately, Hoshiyomi didn't get to fully admire its power—because even this Perfect Susanoo was still a bit too much for Kuugetsu.
She managed to maintain the Perfect Susanoo for less than ten seconds. After just a slight shake of its wings, the entire construct suddenly dissolved into nothing.
Though a bit regretful, both of them were still satisfied. After resting briefly, they returned to Konoha. Hoshiyomi planned to escort Kuugetsu back to the Uchiha compound before returning home.
But upon arriving, they found the Uchiha clansmen strangely excited.
The two exchanged looks, and Kuugetsu grabbed a familiar clansman by the arm, asking:
"Uchiha Kō, what happened in the clan?"
When Uchiha Kō saw Kuugetsu's eyes, his own lit up, but as soon as he glanced at Hoshiyomi beside her, his expression froze oddly. He finally stammered:
"Lady Kuugetsu, we've been waiting for you… you should go see for yourself. Your cousin… he's not going to make it."
After saying that, he gave Hoshiyomi another deep look and turned away.
Seeing this, Kuugetsu felt irritated and confused.
"Even if my cousin has been suffering from illness for years and finally passed away, they should feel sadness. Why does everyone look like they're celebrating? Have they all gone mad?"
At her words, Hoshiyomi's pupils suddenly shrank.
He immediately realized who Kuugetsu's cousin was.
Kuugetsu's cousin… that would be Shisui's father!