Why did Uchiha Kei believe they were now capable of confronting the Nine-Tails?
The answer, unsurprisingly, had to do with his recently unlocked Level 3 Mental Network.
This level came with numerous new abilities—too many to list in detail—so only relevant functions were explained as needed. One of those was the ability called Mental Resonance.
It was complex in technical terms, but put simply, it allowed for the sharing of mental energy with others via resonance.
According to the system, this ability could theoretically only work between users of the Mental Network, due to the need for frequency synchronization.
But in the shinobi world, that was impossible. Kei was the sole user of the Mental Network.
So, he combined it with the power of the Sharingan. By using the intense emotional fluctuations of others within the genjutsu game, he could mimic their mental frequency.
Due to the nature of the Sharingan, this copy-and-paste technique only worked on other Sharingan users.
And while copying mere ocular power didn't mean much—Kei already had access to as many three-tomoe Sharingan as he wanted—the true value was in Mangekyō-level abilities.
In theory, Kei could now replicate Mangekyō abilities by stimulating others to awaken their Mangekyō Sharingan, then linking mentally at that moment.
Why did he go out of his way to help Obito awaken his eyes? Was he some saint?
Not at all. He simply coveted Obito's Kamui. One of the strongest and most broken abilities in the entire Naruto series, Kamui's survivability was unmatched—it was a dream power for any transmigrator.
So once Kei realized he might be able to replicate Kamui—even if he couldn't use it indefinitely—he was determined to get it.
Hence, the extreme operation tonight.
In the end, Obito failed to fully awaken his Mangekyō due to insufficient stimulus. Kei didn't get Kamui—but he did copy something. A portion of Mangekyō-grade ocular power.
Even if it drained Kei heavily, it was enough to use against the Nine-Tails.
Remember: in the original story, Obito suppressed the Nine-Tails before even awakening the Mangekyō. After doing so, the power he wielded—even in a three-tomoe form—was more than sufficient.
With this same level of power, Kei could target the Nine-Tails sealed inside Kushina Uzumaki.
Of course, that wasn't absolute. Online debates from Kei's past life argued that most Mangekyō couldn't actually control the Nine-Tails. Obito's success came from inheriting Uchiha Madara's legacy and having his body rebuilt with White Zetsu parts—making his eye power nearly equivalent to the Eternal Mangekyō. Nᴇw ɴovel chaptᴇrs are published on 𝔫𝔬𝔳𝔢𝔩⁂𝖿𝗂𝗋𝖾⁂𝔫𝔢𝔱
After all, even with Kamui, Kakashi couldn't suppress Naruto's Nine-Tails. He needed Yamato's Wood Style to help.
Still, Kei had faith. He had enough trump cards and gadgets to shake the Nine-Tails a little—to give it a "spiritual jolt," so to speak.
Once the Nine-Tails got a taste of "a bag of rice bears how many floors," it would surely settle down and talk things out—just like when Hashirama controlled it, or when it was sealed inside Mito Uzumaki.
Preparations began. Uchiha Naori returned after making arrangements, and the team began setting up a protective barrier.
If things went south, it would prevent the Nine-Tails from rampaging and damaging the village.
Once everything was ready, in the center of the living room where the barrier formation was drawn, Uchiha Kei and Kushina Uzumaki sat facing each other.
Minato Namikaze sat to Kushina's right, eyes closed, placing his right hand on her abdomen.
Kikyo Uzumaki sat to her left, eyes also closed, simply holding her hand.
The two of them would enter Kushina's seal space by linking their consciousness. Without Sharingan, they needed direct contact.
Minato interfaced with her Four Symbols Seal, and Kikyo relied on bloodline resonance.
As for Kei—Sharingan, activate!
Outside, the Uchiha guards all activated their Sharingan, standing by for any threats.
Once everything was ready, Kei locked eyes with Kushina and unleashed the Mangekyō-level ocular power he had copied from Obito.
The massive chakra consumption almost made him collapse on the spot.
Thankfully, Kei was prepared. He immediately triggered a skill he had received from the system long ago—restoring himself to full strength.
\\[All-Nighter: Active Skill. When activated, keeps the user in a peak mental state for 4 hours. Afterward, all accumulated fatigue hits at once. Cooldown: 72 hours.]
Originally intended for crunch-time game development, the skill now had an unexpected use in the shinobi world—keeping chakra recovery and ocular power regeneration at peak performance.
While technically borrowing from future stamina, and potentially fatal if overused, Kei had found a workaround.
Remember that golden antidote from the platinum chest?
It was a pure system item—usable only by Kei. Stored in the system inventory, it could be activated with a thought.
Thirty uses. Called an "antidote," but it actually nullified all harmful debuffs. It couldn't heal or restore stamina, but it could erase all negative effects unconditionally.
Like the fatigue explosion caused by "All-Nighter." Once the debuff kicked in, the golden antidote would treat it as a removable condition.
Thus, Kei discovered a game-breaking combo.
No matter how much stamina or chakra he burned during those four hours, as long as he used the antidote before time was up—no consequences.
It was like a mutated Golden Experience Requiem!
As long as the golden antidote reached it, death itself could never catch him!
Most importantly, he had thirty of these, and who knew—maybe the system would drop more.
In short, Kei now had the equivalent of a pseudo-Eternal Mangekyō Sharingan. And the abilities weren't fixed—he could copy more as others awakened theirs.
Had he known that Setsuna Uchiha had already awakened his Mangekyō, he would've gone to copy that instead of tormenting Obito.
Why hadn't anyone told him?
Ah yes, the famed Uchiha "inspiring genius" mentality.
Uchiha Setsuna believed that telling Kei would place emotional pressure on him—perhaps even lead him to do something reckless out of guilt.
So, with classic Uchiha melodrama, he decided to keep it secret. He asked others to pass along his Mangekyō and a farewell letter only after his death.
Setsuna believed that when the time came, Kei would understand his intention—and be moved.
That's the kind of emotional brilliance Uchiha are famous for.
Thus, despite the clan already having a Mangekyō user, Kei remained unaware. Thinking no one else could awaken it, he targeted Obito—who canonically unlocked it with just two tomoe.
If he ever found out, Kei would no doubt curse, "Oh, thank (F\\*CK) you, old man!"
In any case, that was the situation.
Now, Kei and his three teammates had entered the seal space housing the Nine-Tails—and came face to face with the strongest Tailed Beast, bound in chains.