Naruto: Reborn as Kakuzu, the Immortal Assassin

Rat. Ox. Tiger. Monkey. Boar. Goat. Snake.

Kakuzu's hands moved in a blur, forming seals with practiced precision.

"Dark Night Walking Technique!"

Whoosh— The lights in the room extinguished instantly. Even the faint glow from outside vanished, plunging everything into total darkness.

The only illumination came from Kakuzu's eyes, gleaming like embers in the pitch-black void.

This technique, a high-level genjutsu, temporarily blinded its target. If properly refined, Kakuzu mused, it might even match the grandeur of the Uchiha's legendary genjutsu prowess.

He reversed the seals, dispelling the technique. The darkness lifted, and Kakuzu leaned against the wall, his breath steadying as he assessed the changes in his body.

The cells of Hashirama Senju had, at last, granted him a glimmer of opportunity. His blood coursed with newfound vitality, his chakra pathways humming with potential. This was the foundation for his continued evolution.

To date, he had mastered nearly all of Tobirama Senju's forbidden techniques—everything except the Flying Thunder God. Even the most complex of them, Edo Tensei, posed no insurmountable challenge.

Of course, the current version of Edo Tensei was far from the perfected iteration seen during the Fourth Great Ninja War. At this stage, the technique lacked precision in reviving targets. Who—or what—it summoned was entirely up to chance: shinobi, civilians, samurai, or something else altogether.

The timeline was equally unpredictable, bringing forth individuals from disparate points in their lives. A revived subject might retain 80% of their peak strength—or as little as 20%. They could even return as infants.

The results could be... awkward, to say the least.

Kakuzu had a theory about these resurrection techniques—whether Edo Tensei, Rinne Rebirth, or One's Own Life Reincarnation. All of them likely required an understanding of the metaphysical concepts of time and space to precisely interact with the Shinigami's domain. Without that, the outcomes would always be inconsistent.

Such mastery, Kakuzu reasoned, was beyond Tobirama's current grasp. These techniques were the work of pioneers, meant to be refined by their successors.

Take the multi-shadow clone jutsu—perfected by Naruto Uzumaki, or the Flying Thunder God—streamlined by Tobirama Senju. And as for Edo Tensei? It would eventually find its master in Orochimaru.

Heh. Tobirama, the "copyright ninja." When you're resurrected, you'd better start collecting royalties—should net you tens of billions. Enough for decades of research.

Back to the matter at hand.

Kakuzu straightened up, leaning forward slightly as his arms extended backward.

Rustle, rustle, rustle—

The black threads of his Earth Grudge Fear technique began unraveling from his body. As the threads spilled out, so too did Kakuzu's "partners."

Releasing them heightened his awareness of his body's internal changes.

The black threads still covered his body as they always had. However, beneath them, a thin layer of newly formed tissue had begun to grow—a fragile but living structure.

This fusion of life and Earth Grudge Fear threads represented the synthesis of rebirth and immortality.

Before long, all his "partners" emerged.

They stood before him, their forms varying in height and build. Mindless entities, they existed solely to follow Kakuzu's commands.

Each partner possessed a heart, and like Kakuzu, the newly grown tissue beneath their black-threaded shells mirrored his transformation. However, Kakuzu could tell the new tissue was still underdeveloped, akin to that of a newborn. Reaching the durability of an adult's would take at least ten years of growth and training.

Not that it mattered. For someone like Kakuzu, time was of little concern.

What intrigued him more was a different development.

Placing a hand over his chest, Kakuzu observed his "partners."

Fire: Partner Alpha, encased in a crimson shroud.

Water: Partner Beta, flowing like liquid.

Lightning: Partner Gamma, crackling with energy.

Wind: Partner Delta, sharp and agile.

Earth: Partner Epsilon, donning a yellowish-brown mask.

Traditionally, the Earth heart always remained within Kakuzu's body. Its defensive properties made it the ideal choice to safeguard his core. Yet today, even the Earth heart had been externalized.

Kakuzu could feel it—another heartbeat, steady and strong.

Thump. Thump. Thump.

A new heart had formed within him.

Unlike the other hearts, this one embodied not an elemental nature but the essence of Kakuzu's forbidden jutsu itself.

This meant that from now on, he had another powerful ally in battle. Where once he fought as five, he would now fight as six.

Kakuzu smirked. His strength had undeniably taken another leap forward.

The emergence of the sixth heart was no mystery.

The successful fusion of Hashirama's cells with Earth Grudge Fear had triggered this evolution—proof of new life being born amidst the conditions of immortality.

Much like the ten thousand White Zetsu, whose artificial lives stemmed from Hashirama's cells, Kakuzu's body now allowed for the emergence of new hearts without rejection.

Satisfied with this result, Kakuzu thought, Not bad at all.

Swoosh, swoosh, swoosh! Under his conscious control, five lifeforms returned to his body in perfect unison. With his new form, Kakuzu decided it was time to prepare for his next steps.

...

A few days later.

In the Senju compound, sunlight poured through the windows, filling the room with warmth and brightness. Senju Tobirama sat cross-legged on the floor, a pen clenched between his teeth as he frowned in deep thought.

Suddenly, the subtle movement of the pen stopped, hanging still in his mouth. With the slightest exertion, Tobirama could have transformed it into a shuriken, ready to strike in an instant.

His sharp, narrow eyes shifted toward the door. Someone had arrived uninvited. He had already sensed their presence, but what puzzled him was the lack of any warning from the guards stationed outside. Closing his eyes, Tobirama focused on the chakra signature.

And then, his eyes shot open.

"Something's off…"

On the rooftop, Kakuzu stood casually, giving a small nod in greeting to Senju Momoka before leaping down to the entrance. He landed effortlessly, coming into Tobirama's line of sight.

"You've grown stronger. Much stronger," Tobirama remarked, removing the pen from his mouth and setting aside his work.

His gaze toward Kakuzu was sharp and serious.

He remembered their battle from years ago. At the time, Tobirama hadn't fully understood Kakuzu's abilities, whereas Kakuzu had thoroughly studied the Flying Thunder God Technique. That fight ended with Kakuzu leveraging his superior intel for victory.

Over the years, Kakuzu's capabilities had gradually revealed themselves, but his power seemed stagnant. Tobirama had assumed Kakuzu had already reached his peak.

But now, seeing him today, Tobirama couldn't help but reconsider.

It was clear that Kakuzu had been honing himself for years, leading to a breakthrough. Tobirama realized his previous understanding of Kakuzu had been incomplete, even flawed.

Most intriguingly, Tobirama sensed there was still a thick veil around Kakuzu—a shroud even his keen perception couldn't penetrate.

Just how strong was Kakuzu now? Even Tobirama couldn't tell.

Picking up on the astonishment in Tobirama's voice, Kakuzu smirked slightly and tilted his head, gesturing toward the courtyard.

"Care to test it outside?" Kakuzu offered. "Talking only gets us so far. A good fight would make it clear."

After all, it had been years since Kakuzu had fought seriously. He was worried he might've grown rusty.

But Tobirama shook his head and returned his focus to the blueprints on the table.

"I'm not going."

Hearing this, Kakuzu scratched his nose awkwardly. He hadn't expected such a blunt refusal.

Tobirama's reason, however, was simple: Hashirama had placed him under strict orders not to leave the compound. If Tobirama dared step outside, Hashirama would break his legs upon returning.

And fighting in the courtyard? That wasn't an option either. If they destroyed the Senju compound, Kakuzu could walk away without a care, but Tobirama? Hashirama would absolutely break his legs for that, too.

Resigned, Tobirama stayed put in his room.

Kakuzu walked in uninvited and sat across from Tobirama. Seeing the usually dignified Tobirama in such a restricted state, Kakuzu couldn't help but chuckle.

"This must be tough for you. Don't worry, it'll pass."

His gaze drifted to the blueprints Tobirama was working on.

"Even as the Senju clan's second-in-command, you still find time to dive into forbidden jutsu research?"

Tobirama didn't look up. He simply let out a lazy "heh."

"Just passing the time by revisiting old, unsolved theories. I doubt this one will ever succeed, though."

Kakuzu raised an eyebrow. Was there really a forbidden jutsu Tobirama couldn't complete? His curiosity piqued, he leaned closer to examine the blueprints.

As he read the title of the technique, his expression shifted.

"This is…!"

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

For each 100 Power Stones +1 Chapter

Read more than +100 chapters and support me on Patreon

Patreon(.)com/Jixo