Obito

"Mangekyō Sharingan."

Uchiha Chen stared straight at the single eye beneath Obito's mask, his face displaying a precise blend of "three parts surprise, three parts confusion, and four parts caution." With his emotions layered perfectly, he delivered an Oscar-worthy performance.

"You can even control a Tailed Beast! The Night of the Nine-Tails from before was your doing, too, wasn't it? Could it be that you are..."

"Correct, it is indeed I."

Uchiha Obito nodded, feigning a weary tone:

"I never expected that after several decades, a descendant of the Uchiha would still remember me.

What I expected even less was that a wielder of the Mangekyō Sharingan would appear within the clan."

"It really is you, that evil Senju Tobirama!"

Uchiha Chen placed a hand on his hip, striking the classic "there is only one truth" pose of a certain pint-sized detective:

"I was suspicious when I discovered that Madara's corpse had gone missing in the village.

You old ghost Tobirama, did you finally turn yourself into this half-human, half-ghost freak through human experimentation because you coveted the power of the Sharingan?"

Obito was so shocked by Uchiha Chen's confident "deduction" that he was momentarily speechless, unsure of how to respond.

"See? I hit the nail on the head, didn't I?"

"I am Uchiha Madara!"

Obito was already growing irritated, but he still controlled his emotions, trying his best to feign the desolation of someone forgotten by the world:

"Does no one in the clan mention me anymore? Heh, Konoha."

"You're really Uchiha Madara? A single Mangekyō Sharingan isn't enough to be convincing. What evidence do you have to prove you are Uchiha Madara?"

Uchiha Chen dropped his previous flamboyant act, squinting his eyes like a fox as he looked Obito up and down, as if trying to see through the face beneath the mask and black robe.

He was spouting nonsense earlier just to distract me and test me. What a cunning brat!

Obito cursed inwardly. Recalling the tone and mannerisms of Uchiha Madara from his memories, he tilted his head slightly, cast a disdainful glance at Uchiha Chen, and let out a cold snort from deep within his throat:

"Believe what you will. I, Uchiha Madara, have never explained my actions to anyone in my life!"

"There we go, that line has a hint of Madara in it. It's just too cliché in its arrogance; it has the skin but lacks the spirit of Madara!"

Uchiha Chen clapped his hands, his eyes full of mockery as a sneer curled his lips:

"Your acting is artificial and slightly over-the-top. And that's not even the biggest point you missed. You're cosplaying Uchiha Madara, yet you didn't bother to learn his life story?

Uchiha Madara's most beloved brother died at the hands of Senju Tobirama. I mentioned Senju Tobirama, even called you Senju Tobirama, and you didn't give any reaction at all?

Unqualified. Absolutely unqualified!"

Watching Uchiha Chen continue to critique him, Obito could no longer suppress the anger and killing intent in his heart, glaring viciously at Uchiha Chen.

[Demonic Illusion: Shackling Stakes Technique]

Metal stakes appeared out of thin air, covering the sky like a torrential rain, stabbing fiercely toward Uchiha Chen.

In the Mental Space, genjutsu—or rather, Yin Release—is the only way to inflict damage upon an enemy.

As it happens, every Sharingan wielder is an expert in this field, and Uchiha Chen was no exception.

[Demonic Illusion: Mirror Heaven and Earth Change]

Uchiha Chen treated the stakes meant to damage his spirit body as nothing, directly unleashing this technique to reflect the genjutsu.

The number of stakes doubled, returning along their original path to stab at Obito. Then, Obito also used Mirror Heaven and Earth Change.

I reflect your reflection of my reflection.

Since both sides possessed Sharingan and genjutsu passed down from the same ancestor, neither could break the cycle.

Finally, unable to endure this childish back-and-forth, Obito changed tactics first.

"Junior, let me show you what a real battle in the Mental Space looks like!"

Although Uchiha Chen had already stripped away his "Madara" disguise, Obito still desperately tried to maintain his "Madara" identity.

Slash!

Obito suddenly pulled a long blade from his own "body" and slashed head-on at Uchiha Chen. With a twist and turn of the blade, a spray of Bloody Mist erupted from Uchiha Chen's neck.

Being slashed in the neck within the Mental Space wouldn't kill him, of course, but every injury to the spirit body caused depletion, requiring the consumption of high-quality Yin Release Chakra—Eye Power—to repair.

"Die!"

A fierce light erupted from the blade in Obito's hand. In an instant, the slashes became as dense as rain. Uchiha Chen dodged and countered with all his might, but he was still caught off guard and took several more hits.

"This feeling..."

Uchiha Chen, now on the defensive, remained as calm as water. While repairing his spirit body with Eye Power, he carefully sensed the sensation of Obito's weapon cutting through his spirit body.

"I understand now!" After being slashed by Obito once more, Uchiha Chen suddenly shouted, bursting into laughter.

"What could you possibly understand?"

Uchiha Obito's voice was cold and sharp. The long blade in his hand attacked Uchiha Chen incessantly, like a pile driver, striving to inflict the maximum amount of damage.

Clang, clang, clang, clang—

For the first time, the sound of crisp, rapid metallic clashing rang out within the sealed Mental Space.

Uchiha Chen blocked Obito's attack with a crooked, charred stick that had appeared out of thin air, then burst into loud laughter.

"Ahahahahaha!

The mystery of Yin Release lies in creating form from nothingness!

By using willpower to imbue high-quality Yin Release Chakra with concepts like 'hardness,' 'sharpness,' or 'blade-like,' one can create the corresponding physical form."

Back in the day, Teacher Kaido from next door helped Luffy upgrade to the Sun God with three strikes of his club.

Today, I, Uchiha Chen, had to take thirty slashes from Obito just to barely grasp Yin Release; my comprehension really can't compare to a protagonist with cheats!

Uchiha Chen looked at Obito, his eyes gradually growing fervent.

He finally realized one thing:

The most precious things about Obito were not his Kamui eye or his body made of Hashirama Cells, but the teachings and knowledge he had inherited from Uchiha Madara.

That was knowledge encompassing Yin-Yang Release, various Uchiha secret techniques, and even the Six Paths Ten-Tails Coffin Seal.

Thus, at this moment, Uchiha Chen made a bold decision.

Uchiha Chen's original plan was to use his replicated permanent Kotoamatsukami on Karatachi Yagura; once Yagura became the Mizukage, Kirigakure, one of the five great ninja villages, would fall into his hands.

Now, he had changed his mind.

He closed his right eye, then covered his left eye with one hand; the pitch-black tomoe began to spin at high speed, transforming into a shuriken-shaped Mangekyō, and an extremely tyrannical Eye Power began to gestate.

[Kotoamatsukami]

With a cooldown time exceeding ten years and an Eye Power consumption dozens of times greater than ordinary ocular techniques, it traded everything for the miraculous power to permanently alter another's will and turn them into one's own puppet.

"What are you doing?"

Sensing something was wrong, Obito threw the long blade in his hand at once, but it was too late.

Because they were inside the Mental Space, Uchiha Chen did not even need to make eye contact with Obito to activate Kotoamatsukami; he only needed to look at Obito's mental projection.

The surging Eye Power poured out like a rushing torrent, transforming into a strange, twisted shadow that instantly linked with Obito's mental projection.

Kotoamatsukami, activation successful.