Naruto: Reborn as Kakuzu, the Immortal Assassin

Tobirama Senju wanted to uncover Kakuzu's true intentions. To do so, he devised a cunning plan using Hashirama's cells as bait, creating a trap hidden in plain sight. Tobirama knew that someone as skilled as Kakuzu would eventually notice this detail and track down the blood sample. That was precisely what he wanted.

The location where the blood was kept had a barrier set up. Any disturbance in Hashirama's blood would immediately alert Tobirama. Now, the bait was laid, it was up to Kakuzu to decide if he had the nerve to take it.

Today, this matter came to a conclusion. Kakuzu lost his job but stumbled upon a treasure. Still, he didn't show any excitement. Holding something so valuable demanded restraint. True to his nature, Kakuzu maintained a calm demeanor.

Over the next few days, some close acquaintances, including Nara Shoroku, came by to visit him.

"Kakuzu, come on, look at the bright side. With your skills, finding another job will be a piece of cake!"

"It was a bit rash of the Hokage to shut down the lab, but trust his judgment."

"If nothing else works out, you could always become a ninja. Starting salary's at least 300,000 ryo a month."

Kakuzu was in his thirties—a middle-aged man suddenly unemployed, with no stable income. All he had left were around 300 rental properties, a famous glass factory, and a hidden gambling den that very few knew about.

Kakuzu rose and thanked Shoroku and the others for their concern before seeing them off. Afterward, he spent the next few days moping in his room. However, each night he would quietly work in his lab, using equipment to refine Hashirama's blood.

His goal was clear: fusion. He didn't need to carve chunks of flesh for testing, his threads of Earth Grudge Fear were more than sufficient. Yet every time the threads merged with the blood, the results disappointed him.

In the experiment vials, the black threads showed minimal vitality. The moment they came into contact with Hashirama's blood, all life within them was devoured completely.

This confirmed two things: the immense power of Hashirama's cells and the stark weakness of Kakuzu's body, apart from his hearts. If he wanted to integrate these cells, there was only one solution—dilution.

After several nights of work, Kakuzu stared at the liquid in the vials with a troubled expression. This was the highest dilution he could manage under his current circumstances—roughly 260 times.

He couldn't help but doubt himself. Diluting Hashirama's blood 260 times? It was practically water at this point. And yet, his black threads still struggled to withstand it.

Was his Earth Grudge Fear really that weak?

Frustrated, Kakuzu spent the next three days smoking in his room. Eventually, he made up his mind.

Five hearts. Five elite jonin. That was the limit of his current strength. But in this ninja world, if he couldn't grow stronger, if he remained stagnant, he might as well be dead.

Thinking of Senju Hashirama and Uchiha Madara—those men who stood at the pinnacle of power—Kakuzu knew he had no choice.

In his previous life, he had been frail and helpless, his days consumed by illness. Having died once already, he no longer feared death. If anything, he feared stagnation more.

With grim determination, he picked up a syringe.

The needle pierced his artery. The plunger of the injector compressed rapidly under his hand.

The liquid flowed through his body like a rushing river, carried along by the black threads of Earth Grudge Fear.

Kakuzu felt a coldness spreading through him, inching its way to his head. He wasn't sure if this was a physical reaction or just his mind playing tricks on him. His body grew colder, and his consciousness began to fade.

Before darkness claimed him, he clung to one thought:

This is my chance to change my fate. I can't let it slip away. I won't let it slip away. If I fail, I would rather die.

Drip. Drip. Drip.

The clock on the wall struck 7 p.m.—the exact time Kakuzu had injected the Hashirama cells.

Three days had passed since then.

Creak.

The door slowly opened.

A cautious head peeked inside.

"Kakuzu-san…"

The voice belonged to Maruboshi Kosuke. Once a six-year-old when Kakuzu took him in, Kosuke was now a teenager and close to graduating from the Ninja Academy. Kakuzu had instructed him to guard the door and let no one in. For three days, Kosuke had faithfully obeyed. But his concern eventually got the better of him, and he decided to check on Kakuzu.

The sight inside made his heart lurch.

Kakuzu sat motionless on the ground, eyes closed and hands limp at his sides.

Panic surged through Kosuke, and his first instinct was to scream. But he remembered his training—he was a ninja. He forced himself to stay calm and cautiously approached Kakuzu.

Kosuke's fear gnawed at him, but he searched Kakuzu's body for any sign of life.

Then, he saw it—a single bead of sweat trailing down Kakuzu's forehead.

Do the dead sweat?

Kosuke wasn't sure anymore. Trembling, he reached out a hand to check Kakuzu's breath.

But before he could—!!!

Swish!

"Uwaaahhhhhhh!" Kosuke let out a strangled cry, nearly scared to death. Before his fingers even brushed Kakuzu's nose, a powerful hand shot out and grabbed his wrist.

He wanted to scream, but before he could let out more than a few syllables, another hand clamped over his mouth.

One minute later...

Kosuke was panting heavily. The grip on his wrist had loosened, and the other hand was gone as well. As he rubbed his sore wrist, he looked up, utterly bewildered. There was no mistake—dead people don't sweat, right? And yet, here was Kakuzu, drenched in sweat that practically steamed in the chilly air.

"Kakuzu-san... are you okay?" Kosuke asked cautiously, finally convinced this wasn't some macabre prank.

Kakuzu wiped the sweat from his brow, a faint smile tugging at the corner of his lips.

"I'm fine. I just had a dream... a very long dream."

That dream, however, had been no ordinary one. It showed Kakuzu a vision of his past lives and present self. He wasn't just the Kakuzu of this world, nor the Kakuzu of his former life. He had become something entirely new—a fresh existence, forged with his own thoughts and will.

With a burning determination to survive from his past life, Kakuzu knew one thing: this time, he wouldn't fall.

When he awoke, a revelation struck him. Immortality wasn't just about eternal life, it was about invincibility. True immortality meant ensuring no one could ever hurt him again. He swore to seize every opportunity to grow stronger, no matter what.

This life, he realized, wasn't a supporting role.

He was the protagonist.

Now that he was awake, Kakuzu's heart was steady. Yet three days and nights of mental battle had taken their toll, leaving him physically and emotionally drained.

"Kosuke, thank you."

Kosuke gave him a small, relieved smile. "Of course, Kakuzu-san. Get some rest. I'll head to the market and grab something to help you regain your strength."

Once Kosuke confirmed everything was fine, he left the room, closing the door firmly behind him.

As soon as the door shut, Kakuzu exhaled deeply, his breaths heavy with fatigue. But despite his exhaustion, there was something he couldn't ignore—something he had to test immediately.

He stood, feeling a strange solidity in his body that hadn't been there before. Raising his hands slowly, he clasped them together, channeling chakra throughout his body with practiced precision.

"Multi-Shadow Clone Jutsu!"

Bang! Bang! Bang! Bang!

Thick clouds of smoke filled the room, and when they cleared, it was packed with identical clones of Kakuzu, each standing ready.

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