Natural Energy

Off the coast of the Land of Waves, three ninjas and five figures stood on the surface of the sea.

"Sage Art: Wind Style: Ultra-Big Ball Rasenshuriken!"

Naruto and his two Shadow Clones raised a giant shuriken together with six hands. It was over a meter in diameter and made entirely of chakra.

"What incredible chakra! You can actually see it with the naked eye!"

Sakura struggled to steady herself. "In terms of power alone, this jutsu has already surpassed S-rank, hasn't it?!"

"But there's no rank higher than S-rank, so this jutsu is still S-rank."

Naruto said, "The Rasengan itself is only an A-rank jutsu, but in theory, as long as you keep pouring chakra into it, its power can keep increasing. However, the more chakra you use, the harder it is to maintain the Rasengan."

"Why didn't you use this jutsu when you fought Orochimaru?"

Sasuke asked, "You should've been able to kill Orochimaru before he 'shed his skin' with this jutsu."

"In theory, yes, but Orochimaru wouldn't have given me the chance to use it in that situation."

Naruto reminded them, "How long have I been standing here? In a real fight, what opponent would just stand there and watch me finish this jutsu? Besides, this jutsu doesn't just consume a huge amount of chakra; it also requires me to refine additional Senjutsu Chakra. If I use it at full power, even I'll lose thirty percent of my chakra."

"True. The chakra cost of this jutsu is terrifying."

Sasuke had watched Naruto form the Rasengan with his Sharingan active the entire time. He now theoretically knew how to do it, but with his chakra reserves, he couldn't even make a Rasengan this big. He might not be able to form one a tenth of the size properly. "Is this the biggest you can make right now?"

"I could make it a little bigger, but there's no need to push it to the limit just to show you."

As he spoke, Naruto threw the Ultra-Big Ball Rasenshuriken into the distance.

The Ultra-Big Ball Rasenshuriken spun rapidly as it surged forward. It moved so fast that in the blink of an eye, it had flown more than a hundred meters.

About fifteen seconds later, the Ultra-Big Ball Rasenshuriken detonated, either after hitting something or after reaching the surface of the sea.

The highly compressed chakra expanded into a sphere, but the lower half was obscured by seawater, leaving only the hemisphere above the sea visible.

A few seconds later, the chakra sphere gradually elongated and spun, stirring up a storm and drawing in seawater. Then it unleashed its energy toward the sky, transforming into a shining pillar of water that shot upward.

The energy discharge lasted about a minute. During that time, seawater swept up into the sky kept falling back down, as if a rainstorm had broken out over a small area.

Watching the "crater" the jutsu had carved into the sea in the distance, Sakura and Sasuke felt a little taste of "powah."

Afterward, the three of them returned to Naruto's secret base.

"Naruto,"

Sasuke asked, "That 'Sage Art' you used just now—did your master teach it to you? Can Sakura and I learn it too?"

"Of course my master taught it to me."

Naruto said, "As for you two, he said you need to make more progress with Qi Refining first."

Sakura asked, "Does Sage Art use up qi?"

"Not qi. It uses Natural Energy."

Naruto explained, "Natural Energy is a kind of energy that exists in the environment around us. Under normal circumstances, it's very difficult to sense. Qi can help us perceive it and also help us control it better. If you add Natural Energy to chakra in a specific ratio while refining it, you get Senjutsu Chakra."

"What's the specific ratio? What happens if you add too much or too little?"

Sakura asked, "If you can't control the Natural Energy properly, could something dangerous happen?"

"You have to precisely combine equal amounts of Natural Energy, physical energy, and mental energy to refine Senjutsu Chakra. If there's too little Natural Energy, you won't be able to refine Senjutsu Chakra. But if the proportion of Natural Energy is too high, our bodies will turn to stone."

Naruto said solemnly, "Also, remember this: if you absorb too much Natural Energy into your body at once and fail to control it, your body will turn to stone even if you don't use it to refine chakra."

"Turn to stone?!"

Sakura was shocked. "That's way too dangerous!"

Sasuke said nothing, but his expression suggested he felt the same way.

"That's why you need to get more familiar with Qi Refining. Qi can suppress Natural Energy's petrifying effect. As long as you have enough qi inside your body, you won't turn to stone even if you accumulate a lot of Natural Energy."

Naruto explained, "And don't think absorbing Natural Energy is easy. There's already a lot of Natural Energy all around us right now, and you've both learned Qi Refining. But can you sense it?"

No.

Before, they hadn't known Natural Energy existed, so it was only natural they hadn't sensed it.

Now they both knew it existed, but even when they focused their minds and tried to sense it, they still felt nothing.

"It's normal that you can't sense it yet. How long have you been practicing Qi Refining?"

Naruto said, "It took me five years from when I started refining qi to when I could sense Natural Energy and finally refine Senjutsu Chakra. Even if you're both smarter than me and more talented at Qi Refining, it'll still take a year or two, right?"

"True. I was too impatient."

Sasuke took a deep breath and slowly exhaled. "I've been gradually realizing how big the gap between us is, and it's making me a little anxious."

"This... Wait."

Naruto suddenly closed his eyes. After a long while, he opened them and asked, "My master said he has a special training method that can make you much stronger in a short time, but the process is pretty grueling. He asked me to see if you'd like to try it."

Sasuke was about to answer immediately, but a sudden chill made him pause. He asked one more question: "Have you tried it?"

"No."

Naruto answered honestly. "I wanted to try it back then, but my parents thought I was too young and there was no need to rush. They asked my master to switch me to a more time-consuming, ordinary training method."

"Um, what exactly is the cost?"

Sakura asked hesitantly. "Does it drain your life or something?"

"No. My master said it's a mental trial. It won't harm your body or drain your physical potential."

Naruto relayed his words. "But it's pretty brutal, so you have to prepare yourself mentally. If you can't make it to the end, you might suffer a mental breakdown. That's the biggest cost."

"A mental trial..."

Sasuke was inclined to accept, but the chill he'd felt a moment ago still bothered him. "Can you explain exactly what the training involves?"

Naruto closed his eyes and communicated with his master for a while. Then he opened them and said, "Simply put, your mind is sealed away through Sealing Jutsu. Then, since time flows differently inside the Sealing Space than it does outside, your mind is pushed to its limits in a short time."

"That doesn't sound all that brutal."

Sasuke relaxed a little. "How exactly do they train your mind inside the Sealing Space?"

"The exact training method changes depending on each person's thoughts and perceptions. You'll only know once you experience it yourself."

Naruto looked at Sasuke. "So, want to give it a try?"

After a couple of seconds' hesitation, Sasuke answered decisively, "Yes. Let me try!"