The Rasengan is a signature ninjutsu commonly used by Naruto Uzumaki, the main character in Naruto. It was originally developed by the Fourth Hokage, Namikaze Minato, who was inspired by the Tailed Beast Bomb. He spent three years creating it, and later, his son Naruto perfected and popularized it.
The technique follows the same concept as the Tailed Beast Bomb: condensing chakra into a compact sphere to strike the opponent. Upon impact, it not only causes serious damage but also disrupts the enemy's chakra flow temporarily.
For Kurosawa Raion, the biggest advantage of this technique is that it doesn't require hand seals.
Its essence lies in concentrating chakra into the palm, making it rotate rapidly in multiple directions, and compressing it into a dense, spinning ball of energy.
Eventually, it can be combined with elemental chakra—like wind—to evolve into more advanced forms, such as Wind Release: Rasenshuriken, which greatly enhances its destructive power. But that's a story for another time.
For now, Raion began training with the technique based on the method taught by Jiraiya in the original Naruto.
He focused his chakra into his hand, attempting to form a rotating sphere and create multi-directional chakra flow at high speed.
The results? Disappointing.
He couldn't even form a stable chakra ball, let alone a Rasengan.
Frustrated, Raion asked the system for help. The system responded with a very logical explanation:
"First, your chakra control is still weak. Second, forming a basic Rasengan requires 200 chakra points. Your current maximum is only 100."
Raion immediately understood. If he wanted to perform the Rasengan, the first step would be mastering chakra control. The chakra capacity, he assumed, would increase naturally as he trained and progressed.
Drawing on his memories of the Naruto series, he recalled two classic chakra control exercises:
Focusing chakra to the soles of your feet to climb trees.
Walking on water using chakra.
Since he was surrounded by sea, he had no trouble picking the second method.
He chose a shallow part of the coastline, where the water only came up to his knees. He carefully gathered chakra under his feet and stepped forward—
SPLASH—his feet sank straight into the water. He hit the seabed instantly. Thankfully, the water wasn't deep, and only his pant legs got soaked.
Still, he didn't give up.
Over and over again, Raion practiced. For about an hour, he repeated the attempt. Eventually, he could walk shakily across the water's surface.
For most people, this would be considered rapid progress. Raion knew it wasn't something that could be mastered overnight. Plus, his chakra reserves were nearly empty.
He returned to the ship, raided the cold room, cooked up some meat and vegetables left behind from earlier hunts, and ate his fill. Afterward, he took a quick nap to recover his stamina.
When he woke up, Raion felt completely refreshed—his body was full of energy, and his chakra was back to full capacity.
He headed toward the shallow sea again.
But something blocked his path—a massive creature had emerged from the forest.
It was a two-tailed saber-toothed lion, over six meters long. Two sharp fangs protruded more than twenty centimeters from its lower jaw, and its golden eyes gleamed with bloodlust. Its muscles rippled beneath its fur, and its claws scraped the ground as it stared Raion down.
This beast was far more dangerous than Mochi's lion, Richie. Its gaze alone was more intimidating, and it was clearly several times stronger.
Later, Raion would learn that this species—the Double-Tailed Saber-Toothed Lion—was incredibly rare in the One Piece world. Vicious and bloodthirsty by nature, it would attack any living creature on sight. And if starving, it wouldn't hesitate to turn on its own kind.
Judging by its appearance and the drool dripping from its jaws, this one hadn't eaten in days. Its red, hungry eyes locked onto Raion like prey.
Any ordinary person would've frozen in fear—or dropped dead from panic.
Raion, however, scratched his head casually and muttered, "Yep. Definitely One Piece… What a bunch of freaky beasts."
His nonchalance only enraged the lion further. With a deafening roar that whipped up gusts of wind, it charged toward him.
Raion moved in a flash, dodging to the side. He summoned chakra—electricity crackled violently around his body as he launched his counterattack:
Lightning Release: Chidori Style!
Thunder surged from his hands as he leapt forward. The lion was struck head-on, convulsing in place as its muscles seized. Dark scorch marks spread across its fur. The beast roared in pain, then collapsed to the ground with a heavy thud.
Dead.
The smell of charred meat wafted into the air.
Raion looked at the body, scratched his head again, and muttered, "Well, I was running out of food. Let's hope you taste as good as you smell…"
As the sun began to set, he dragged the lion's body onto his boat. The meat had already been half-cooked from the lightning damage. He roasted the rest and sat down to enjoy his meal.
"Mmm… this is delicious," he said, smiling to himself.
Sitting alone at the table, slicing meat with a knife and fork, Raion looked genuinely content.
In his previous life, aside from being an anime enthusiast, he had also been a serious foodie. Good food always put him in a great mood.
After his feast, he left the messy dishes behind and went to bed.
The next morning, just as dawn began to break, Raion woke up feeling strange.
Stronger.
His body felt charged with power, as if he had gained several hundred pounds of raw strength overnight.
A notification from the system appeared:
"Your chakra limit has increased to 300. Current chakra: 300/300."
Raion was stunned. "Huh? Why?"
The system answered:
"The lion you ate yesterday was a Greyhorn—an extremely rare species of Double-Tailed Saber-Toothed Lion in the One Piece world. Its meat activates your cells, boosts your immune system, and increases physical strength.
In the Naruto System, this translates into a significant increase in chakra.
Additionally, the experience you've gained through recent training has helped raise your chakra reserves."
Raion could hardly believe it. He had gotten stronger just by surviving and training—and by sheer dumb luck in finding and defeating that lion.
Excitement surged in his chest.
With every step, he was getting closer to becoming truly powerful...