Uchiha Setsuna had indeed seen this before. As an old relic of a man, he knew many things. He had personally witnessed someone using Mangekyō Sharingan abilities while still in the three-tomoe Sharingan stage.
That person was none other than Uchiha Madara's younger brother, Uchiha Izuna.
He had once, in a fit of emotion, activated a Mangekyō ability before actually awakening the Mangekyō Sharingan. Although the effect wasn't as strong as it would be after fully unlocking the Mangekyō, it still worked.
His case proved that Mangekyō abilities could sometimes be accessed without formally reaching the Mangekyō stage—under special conditions.
In fact, a future Uchiha would also display this anomaly: Uchiha Obito, the man whose Kamui made us all cry.
In the original story, Obito, buried under a massive boulder, unintentionally activated his Mangekyō ability, allowing him to enter a phase-like state and avoid being crushed. This led to his rescue by Uchiha Madara.
Furthermore, Mangekyō abilities didn't always require the Mangekyō to manifest. During the Fourth Great Ninja War, Uchiha Madara used a base form of Susanoo without having activated his Mangekyō Sharingan.
And then there was Indra, son of the Sage of Six Paths and Madara's previous incarnation—who could use a complete-body Susanoo without even unlocking the Mangekyō, at least according to the manga.
Absolutely ridiculous.
So Uchiha Setsuna's claim that Uchiha Kei could use a Mangekyō ability with a single-tomoe Sharingan didn't seem absurd at all.
After hearing Setsuna's explanation, the other Uchiha were struck with realization. They looked at Uchiha Kei with a mix of admiration and pity—it was a complicated emotion.
According to Setsuna, Kei clearly had the potential for the Mangekyō. Unfortunately, his poor shinobi talent and diluted bloodline kept him stuck at a single tomoe.
Even someone like Uchiha Fugaku, known for overthinking, was already crafting a theory for Kei's ability. He imagined that Kei, ostracized and under constant emotional strain, had finally broken through under pressure and awakened a Mangekyō-level power with a single tomoe.
And yet, despite all that, Kei still only had one tomoe. No signs of progress.
Heaven, why must you be so cruel to Kei-dono?
Thinking this, Fugaku and several others couldn't bear to look directly at Kei anymore.
To them, Kei's life was tragic. If it were any other Uchiha, they'd probably prefer death.
But such was the Uchiha worldview.
And for that reason, they respected him even more—what incredible inner strength. Truly worthy of being called Kei-dono!
Yes, among the clan's elders, some had already begun referring to him with honorifics in their hearts.
Pure headcanon power—undefeated!
As for Kei himself, while he found Setsuna's analysis a bit far-fetched and far from the truth, this interpretation was fine.
The important thing wasn't the origin of the technique, but the reason it couldn't be passed on.
So Kei followed Setsuna's lead and nodded with a look of realization. "I see… So that's what it was. I'd been wondering why my eye suddenly gained a power I couldn't comprehend. I used that force, combined it with my concept, and created a genjutsu-based game."
This statement solidified the story that he'd activated a Mangekyō ability with a single tomoe.
Setsuna nodded again but now wore a stern expression. He spoke with concern, "Kei-dono, since it's derived from the Mangekyō, you should avoid using it too much. Otherwise, you may lose your eyesight."
Hearing this, the gathered Uchiha all looked grave.
To them, the truth about the Mangekyō Sharingan wasn't a secret. They knew its overuse led to blindness.
If Kei's power truly connected to the Mangekyō, then that price might also apply.
To that, Kei shook his head. "While I was surprised to learn that overusing the Mangekyō can cause blindness, rest assured, Elder Setsuna—my secret technique only borrows the unique properties of the Sharingan. It doesn't involve direct dōjutsu use, so my eyesight is unaffected."
"On the contrary, the more I use it, the more benefit I gain. And the more people who play the game, the greater the feedback I receive."
"In that case, I must use it often. And more importantly—I have to spread it. I want as many people as possible to participate."
He paused, then added with determination:
"And it can't be limited to the Uchiha clan!"
The truth was out!
Suddenly, the mood shifted. The gathered Uchiha looked alarmed. One even shouted "No way!" and others quickly agreed—this was a clan secret technique! How could outsiders be allowed to use it?
One particularly hot-blooded member was already visibly furious.
But Kei just smiled calmly. "I know you're all anxious—but don't be. Even with the same genjutsu game, there can be massive differences between how Uchiha and outsiders experience it."
That got their attention. The room calmed as they awaited his explanation.
Kei didn't hold back.
"It's simple. Since it's a genjutsu game, the sensory input can be controlled. For the Uchiha, the experience can be fully immersive—indistinguishable from reality—maximizing our bloodline potential."
"But for outsiders, the realism can be scaled down. We can reduce or eliminate pain, for instance. To them, it really would just feel like a 'game.'"
The Uchiha nodded thoughtfully. That kind of distinction… actually sounded reasonable. It still felt a little wrong, but as Lu Xun once said, the broken-window effect never goes out of style.
Still, Kei followed up with something that made them uneasy again:
"Of course, while that differentiation is possible, I believe the fully immersive version should be released—so that other ninja clans and even civilian shinobi can enjoy it too."
Now they really didn't know what to feel. Kei clearly had a knack for stirring emotions.
Finally, Uchiha Masanobu, the clan head, spoke with gravity:
"Kei-dono, you've proven your wisdom and brilliance. I trust there is meaning behind your actions. So, would you tell us—why are you doing this?"
Kei was very satisfied with that setup. He'd prepared for this moment years ago.
"Everyone, please believe me. Everything I do is for the Uchiha."
"I want us to claim a real seat at the table in the Hidden Leaf leadership. To reclaim the honor and status we rightfully deserve."
"And more than that—I want the Uchiha to have a shot at claiming the title of Hokage!"