Naruto: Tobirama Reborn, Invincible in the Ninja World

The operating room echoed with sporadic noises.

Uchiha Itachi lay on the surgical bed, enduring the invasive effects of transplanted Hashirama cells. Beads of sweat glistened on his forehead as his body battled the powerful, corrosive energy coursing through him.

"Tsk, tsk, tsk," Tobirama murmured, narrowing his eyes. As a Impure World Reincarnation, it had been a long time since he'd felt physical sensations, but watching Itachi's struggle seemed to stir some distant memory.

"Granduncle, what's with that expression?"

Tsunade raised an eyebrow, noticing a subtle change in Tobirama's demeanor. Since his revival, he'd been oddly more approachable, even showing hints of humor.

A sharp hiss of breath broke the momentary pause. On the bed, Itachi clenched his jaw as though a thousand ants were gnawing away at his flesh, a pain far worse than mere physical torment. Yet, compared to the agony of raising a blade against his own clan, against his own parents, this was almost bearable.

He exhaled deeply and steadied himself. His face regained its composure as he allowed the Hashirama cells to reconstruct his body from within. Despite his outward calm, the cold sweat dripping from his temples betrayed the intensity of his ordeal.

It was unclear how much time had passed when Itachi abruptly sat up on the hospital bed.

"Did it work?" Tsunade let out a relieved sigh and cast a knowing glance at Tobirama, as if to say, I told you so.

Tobirama gave her a thumbs-up of acknowledgment before stepping toward Itachi.

"Itachi, how do you feel?"

Looking up, Itachi did something rare—he smiled.

"Hokage-sama, Tsunade-sama, I've never felt better," he replied, his voice steady and calm. "The illness that tormented me is gone. My chakra reserves feel significantly expanded, and there's a new, unfamiliar strength coursing through me."

Tsunade approached him, placing a hand gently on his back to confirm his condition.

"You're right. Your body seems to be in perfect condition now," she noted, her brow furrowing slightly. "But your eyes… something's changed about them."

Tobirama's expression darkened slightly as a theory began to form. Itachi had transplanted Shisui's eyes before. Was this related?

The Uchiha clan had a long history of intermarriage, with members often sharing close blood ties. Shisui and Itachi could very well have been distant relatives. But that raised a critical question—only the Mangekyō Sharingan of direct blood relatives could merge to awaken the Eternal Mangekyō. What was happening here?

"Itachi," Tobirama asked with deliberate curiosity, "do you feel any changes in your vision?"

Itachi's Sharingan activated, the three tomoe spinning before rapidly morphing into the intricate shuriken-like design of his Mangekyō Sharingan. At first glance, it seemed unchanged, but Itachi's expression shifted.

"Hokage-sama...," he began, his voice tinged with astonishment. "I think I understand the change, but I can't explain it in words. Would it be possible to demonstrate it in an open area?"

Tsunade frowned. "Hey, Uchiha brat, you just had a major surgery involving my grandfather's cells. Don't tell me you've already recovered!"

"I assure you, Tsunade-sama, I'm fully healed," Itachi replied respectfully.

Tsunade huffed, activating her medical ninjutsu to verify his claim. After a moment, she sighed and waved him off.

"Fine. But if you collapse, don't blame me."

...

In the Forest of Death

Itachi and Tobirama stood in a clearing, the latter observing with keen interest.

"Hokage-sama, please watch carefully," Itachi said, activating his Mangekyō Sharingan.

The crimson glow in his eyes intensified, and blood trickled down his cheeks. Orange chakra surged around him, quickly forming a skeletal frame. The structure grew, layering with muscles and flesh until it became a towering humanoid figure.

Finally, armor manifested over the construct—a full suit of crimson armor, a giant shield resembling the Yata Mirror, and a gleaming blade in its hand: the Totsuka Sword.

This was Susanoo—Itachi's fully-realized version, but Tobirama immediately noticed something peculiar.

Compared to Madara's towering, hundreds-of-meters-tall Susanoo, Itachi's version stood at a mere fifty meters, appearing almost diminutive in comparison.

Still, the sight was awe-inspiring.

"Hokage-sama, this is my limit," Itachi panted, the orange giant dissipating as he knelt to the ground.

"After transplanting Shisui's eyes, I can now access a new phase of Susanoo," he explained. "But the chakra cost is immense. Without Hashirama's cells, I wouldn't have been able to sustain it for even a moment."

Tobirama stroked his chin thoughtfully. "Fascinating. Historically, only siblings like Madara and Izuna, or Sasuke and Itachi, could achieve the Eternal Mangekyō. Yet your situation proves otherwise."

"This isn't the Eternal Mangekyō," he continued. "It's something new—a variation triggered by transplanting another Uchiha's eyes, even without a direct bloodline. While it grants access to the Susanoo, its strength is clearly diminished, and the chakra drain is severe."

Itachi nodded. "My visual powers consume very little energy, but the chakra demand for sustaining this form is overwhelming."

Tobirama smirked faintly.

"Even so, your potential has increased dramatically. The illness that once hindered you is gone, and you've gained access to this new level of power."

As the two departed the forest, Tobirama couldn't help but wonder:

What else could arise from this new path of evolution for the Uchiha?

----------------

I have a new fanfic about Kakuzu, honestly, I personally like it a lot, if you are interested, click on my nickname under the title of the fanfic

Pls Drop some Power Stones

Read more than +80 chapters and support me on Patreon

Patreon(.)com/Jixo