The Rasengan, a signature ninjutsu of Naruto Uzumaki, the protagonist of Naruto, was originally developed by the Fourth Hokage, Minato Namikaze, who drew inspiration from the Tailed Beast Bomb. It took him three years to complete.
Like the Tailed Beast Bomb, the Rasengan condenses chakra into a dense, spinning sphere that can cause devastating damage upon impact. Not only does it deal physical destruction, but it also disrupts the target's chakra flow.
For Kurou, the biggest advantage of this jutsu was clear: it didn't require hand seals to perform.
Its core principle lay in concentrating chakra into one's palm, then compressing and rotating it in multiple directions at once, creating a compact, high-density chakra sphere.
Later on, elemental chakra could be added to enhance it, like Wind Release, which transformed it into the formidable Wind Release: Rasenshuriken, exponentially increasing its destructive power.
But that was for later.
Kurou began training the Rasengan using what he remembered from the anime, specifically, the method Jiraiya had used to teach Naruto.
He focused chakra into his palm, attempting to gather it into a ball. Then, he tried to force it to spin in different directions.
The result?
Let's just say, it didn't go well.
He couldn't even form a proper chakra sphere, let alone a Rasengan.
Frustrated, he asked the system for guidance.
The system replied with a calm explanation:
[First, your chakra control is still very poor. Second, even the most basic Rasengan requires 200 chakra to perform. Your current max chakra is only 100.]
That made things clear. Before he could use the jutsu, he had to master chakra control. The chakra cap would eventually rise in time.
From his knowledge of the original series, Kurou recalled that there were two main training methods for controlling chakra:
< Focusing chakra to the soles of the feet to climb trees.
< Focusing chakra to walk on water.
Since he was surrounded by ocean, he naturally chose the second method.
He made his way to a shallow patch of sea near the island, where the water only reached his knees. Carefully, he focused chakra into his feet and stepped forward.
Splash. He sank straight down.
Luckily, the water wasn't deep, so only his pant legs got soaked.
But this was just the beginning.
He kept practicing, again and again.
After an hour of trial and error, Kurou finally managed to walk shakily atop the surface. It wasn't graceful, but it was progress.
For a normal person, this would already be impressive progress. Kurou understood this wasn't something that could be mastered overnight. Besides, he had nearly exhausted his chakra.
So, he returned to the ship, raided the cold storage for meat and vegetables, cooked a hearty meal, and took a well-earned nap to replenish his energy.
By the time he woke up, he felt completely refreshed, mind clear, body light. His chakra had fully recovered to 100/100.
He headed out again toward the shallow waters.
But on the way, something large blocked his path in the forest.
A lion, six meters long, with two tails. Beneath its jaw were two saber-like fangs, each over twenty centimeters long, glinting like blades.
The beast stared him down, its posture low, ready to pounce. Its eyes were sharp, far sharper than that of Mohji's lion Richie, and its aura exuded raw killing intent. Its strength likely dwarfed Richie's several times over.
Kurou would later learn that this creature was known as a Two-Tailed Saberfang Lion, a rare and vicious predator in the One Piece world. It was known to attack anything that moved, and if hungry enough, even devour its own kind.
Judging by its current state, it hadn't eaten in days. Its eyes glowed red, and drool dripped from its jaw as it stared hungrily at Kurou.
Faced with such a terrifying predator, most people would have frozen on the spot in fear.
Kurou, on the other hand, scratched his head casually.
"Huh. Definitely the One Piece world. I've never seen a creature like this before."
The lion took that as a provocation. Already short-tempered, Kurou's nonchalance only enraged it further.
It let out a bone-shaking roar and charged, kicking up a storm of leaves and dust in its wake.
Kurou sidestepped its charge with a swift movement, lightning crackling across his body as he activated his jutsu,
Lightning Release – Chidori Stream!
His body surged forward, wrapped in electric light, and slammed into the beast.
The lion froze mid-pounce, spasming violently. In moments, black scorch marks spread across its fur, and with a final, anguished roar, it collapsed with a heavy thud.
Dead.
A clean, one-sided victory.
From the lion's charred corpse rose the distinct scent of roasted meat, residual heat from the lightning technique.
Kurou walked over and scratched his head again.
"Well, I was out of food anyway. Guess you'll be tonight's dinner. Hope you taste as good as you smell."
As the sky began to darken, he hoisted the lion's body onto the ship. Its meat was already half-cooked from the electricity. Kurou roasted it over fire and dug in.
"Mmm... surprisingly good!"
Sitting at the table alone with a knife and fork, Kurou ate to his heart's content.
In his past life, besides anime, his other obsession was food. A self-proclaimed gourmet, nothing made him happier than a satisfying meal.
After feasting to the point of leaving the table in a mess of bones and grease, Kurou yawned and headed to bed.
The next morning, just as the sky began to brighten, Kurou awoke feeling… different.
Stronger.
As if his entire body had been infused with raw energy.
Then came the system notification:
[Your chakra limit has increased to 300. Current chakra: 300/300.]
Huh?
Why?
The system explained:
[Yesterday, you consumed the flesh of a spirit beast, a rare Two-Tailed Saberfang Lion. In the One Piece world, these creatures are incredibly scarce. Eating their meat can activate your cells, boost immunity, and greatly increase stamina. In this Naruto system, that translates to a significant rise in chakra capacity.]
[Also, the training you've accumulated these past few days has helped elevate your chakra reserve.]
So that was it.
Kurou couldn't help but marvel at his good fortune.
His heart raced with excitement.
This meant one thing.
He was getting closer and closer to the realm of true power.
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150 P.S = 1 Extra Chapter