The Rasengan is a ninjutsu commonly used by Naruto Uzumaki, the protagonist of Naruto. It was originally developed by the Fourth Hokage, Minato Namikaze, inspired by the Tailed Beast Bomb. Later, it was further refined and perfected by his son, Naruto.
The principle behind the Rasengan is similar to that of the Tailed Beast Bomb — compressing and rotating chakra into a dense, high-speed spinning sphere that delivers a devastating blow upon impact. Not only does it cause severe damage to the target, but it can also disrupt the enemy's chakra flow temporarily.
For Raion, the biggest advantage of this technique was that it didn't require hand seals, which meant he could learn it without any inherited bloodline or advanced techniques.
The essence of the Rasengan lies in concentrating chakra into the palm of the hand and making it rotate at high speed in multiple directions simultaneously, creating a spinning ball of compressed chakra.
Later, attributes can be added to the chakra — for example, wind chakra — resulting in techniques like the [Wind Release: Rasenshuriken], which multiplies its destructive power exponentially. However, that was a goal for the future.
For now, Raion was relying on the method Naruto learned from Jiraiya in the original series.
He gathered chakra in his hand, attempting to form a perfect sphere, while trying to rotate the chakra streams in different directions at high speed.
The result was obvious.
Not only was Raion unable to form a proper Rasengan, but he found that even creating a stable chakra ball was incredibly difficult.
Frustrated, he asked the system for guidance. The system calmly explained:
"First, your chakra control is still very weak. Second, forming even the most basic Rasengan requires at least 200 chakra points, while your current limit is only 100."
Raion immediately understood — to master this ninjutsu, he first needed to improve his chakra control, and his chakra pool would have to grow significantly in the future.
Based on his memory of the original series, there were two basic training methods to improve chakra control:
Gathering chakra at the soles of the feet to climb trees.
Gathering chakra on the feet to walk on water.
Since he was surrounded by the sea, Raion chose the second method without hesitation.
He moved to the shallow waters near the island, where the sea barely reached his knees, and began focusing chakra into his feet before stepping onto the surface.
The result? He immediately sank, splashing into the water up to his calves. Fortunately, it wasn't deep, so only his pants were soaked.
But this was just the beginning. He continued to practice, over and over.
After about an hour of effort, Raion was able to stand shakily on the water, his balance still unstable but improving.
For an ordinary person, this kind of progress would have been considered incredibly fast. Raion understood that mastery wouldn't come overnight. Moreover, this training quickly drained his chakra, leaving him exhausted.
He returned to the boat, raided the cold storage for food, and had a hearty meal before taking a short nap to replenish his energy.
When he woke up, Raion felt refreshed, his chakra restored to full capacity.
He decided to return to the shallow waters for another training session.
However, as he made his way toward the shore, he was suddenly blocked by a massive figure emerging from the forest.
It was a two-tailed saber-toothed lion, over six meters long, with sharp, blade-like fangs each more than twenty centimeters long.
At that moment, the beast stared at Raion with blood-red eyes, ready to pounce at any second. Its presence was even more intimidating than Moqi's lion, Richie — this creature was far more powerful and ferocious.
Later, Raion learned that the two-tailed saber-toothed lion was a rare and vicious predator, known to attack any living creature it saw. When starving, it would even devour its own kind.
Judging by its appearance, this particular lion hadn't eaten in days. Saliva dripped from its jaws as it locked its predatory gaze on Raion.
For an ordinary person, just facing such a fearsome creature would have been enough to cause paralysis from fear.
But Raion simply scratched his head and muttered,"This really is the world of One Piece… Even the wildlife is like something out of a nightmare."
The lion, as if angered by Raion's casual remark, roared furiously, its voice like a thunderclap. A violent gust of wind followed as it charged straight toward him.
Raion swiftly sidestepped, dodging the initial attack, and let his chakra surge through his body. Lightning crackled across his skin as he shouted:
"Lightning Release – Chidori Current!"
In a flash, his body was wreathed in brilliant arcs of lightning. He lunged forward, the current surging into the beast. The lion's entire body convulsed violently as black scorch marks spread across its fur. With a final, agonized wail, it collapsed onto the ground, lifeless.
It was a one-sided battle.
The smell of burnt meat rose from the lion's carcass, the result of the high-temperature lightning attack.
Raion stood over the massive creature and scratched his head."Well, I was running low on food anyway… You'll make a fine dinner. I just hope you taste as good as you smell."
It was already evening, so Raion hauled the carcass back to his boat. He cooked the already half-roasted meat, savoring the meal as he ate.
"Mmm… Not bad at all."
Sitting alone at the table with a knife and fork, he entertained himself with the feast.
In his previous life, Raion had not only been a huge anime fan but also a dedicated foodie. Good food always lifted his mood.
After eating his fill, he left the messy plates and dishes on the table and went straight to bed.
The next morning, as dawn broke, Raion woke up feeling unusually energized. His body felt stronger, as if raw power surged through his muscles.
Just then, the system's voice rang out:
"Your chakra limit has increased to 300. Current chakra: 300/300."
Raion blinked."Wait, what? Why did it increase?"
The system explained:"The lion you ate yesterday was a rare two-tailed saber-toothed lion. Eating its meat activates your cells, strengthens your immune system, and enhances your physical abilities. Within this Naruto system, that translates to a substantial increase in chakra capacity."
"Not only that," it continued, "but your recent training has also contributed to this boost."
Raion grinned, unable to hide his excitement."So it's true… I'm one step closer to becoming strong enough to stand at the top."