Yamanaka Tohru's Sage Mode

After that, Yamanaka Tohru kept pouring Nature Energy into the Yin Seal. It took nearly ten days for the Nature Energy inside the Yin Seal to reach capacity.

Each time Yamanaka Tohru separated out the special Nature Energy, the amount of Nature Energy it drew in from the outside world varied. It wasn't fixed, so the process took three days longer than he had expected.

Even so, Yamanaka Tohru couldn't help marveling at the terrifying power of nature. It took a person at least two years to fill the Yin Seal by accumulating Chakra, but only ten days to fill it with Nature Energy.

Jiraiya, however, looked thoroughly unimpressed by Yamanaka Tohru's explanation. In his view, filling the Yin Seal with Nature Energy was completely different from a ninja filling it by accumulating Chakra.

Since there was no limit to the amount of Nature Energy available, while a ninja's Chakra was finite. And Chakra could be used to perform ninjutsu, making it far more useful than Nature Energy. As far as Jiraiya was concerned, a Yin Seal filled with Chakra was much more practical than one filled with Nature Energy.

As Yamanaka Tohru poured a vast amount of Nature Energy into the Yin Seal, he gradually understood Jiraiya's point. Just as Jiraiya had said, Nature Energy was inexhaustible.

No matter how much Nature Energy Yamanaka Tohru used up on Mount Myōboku, it never seemed to diminish.

Once the Yin Seal was full, Yamanaka Tohru entered Ice Release and released the Nature Energy stored in the Yin Seal. It flowed in through his arm.

Yamanaka Tohru used Water Ripple and Ice Seal without spending any Chakra; then he used Water Dragon Bullet, and Ice Seal still consumed no Chakra.

Afterward, Yamanaka Tohru shut off the flow of Nature Energy from the Yin Seal. He had left it open for about ten minutes, and it seemed that roughly one-fifth of the Nature Energy inside had been used up. Most of it had dissipated into the air, and only a small portion had been put to use.

In other words, after spending ten days storing Nature Energy, Yamanaka Tohru could use Ice Release for about fifty minutes without spending any Chakra.

The problem that had plagued Yamanaka Tohru for nearly four years—the huge Chakra cost of his Ice Seal techniques—had finally been solved.

With the problem of Ice Release resolved, Yamanaka Tohru decided to start training in Sage Mode.

Sage Fukasaku hadn't been able to enter Sage Mode mainly because he absorbed Nature Energy from the outside world too quickly.

Yamanaka Tohru couldn't fuse his physical energy, spiritual energy, and Nature Energy in a 1:1:1 ratio in time, so he couldn't produce Senjutsu Chakra.

So Yamanaka Tohru wanted to try combining an equal amount of physical and spiritual energy with that special Nature Energy, to see whether he could produce Senjutsu Chakra. If he could, he would open the Yin Seal to replenish the Nature Energy he used up.

In the original story, Sage Fukasaku had said that because ninjas used ninjutsu, it was easy for them to distinguish between physical and spiritual energy. After training, Yamanaka Tohru could do it too.

He guided physical and spiritual energy in amounts roughly equal to that Nature Energy, controlling all three as they merged.

Once the three energies were each at one-third, they began to slowly fuse. A special kind of Chakra was born inside Yamanaka Tohru.

"Is this Senjutsu Chakra?" Orange-red markings began to appear around Yamanaka Tohru's eyes. Since he had sensed the natural Chakra using Mount Myōboku's Toad Oil, his Sage markings looked just like Naruto's.

Yamanaka Tohru felt the changes in his Chakra. Just as the original story had described, Sage Mode's enhancement was indeed significant. His perception and physical agility were greatly improved.

Yamanaka Tohru activated Lightning Release Chakra Mode and simultaneously released the Yin Seal. After testing it, he found that Lightning Release Chakra Mode powered by Senjutsu Chakra gave him a tremendous boost in speed and strength, making him even faster than in Ice Lightning Mode.

"Sage Art: Chidori!" Yamanaka Tohru infused Senjutsu Chakra into Chidori. Its size and power both increased, and even the sound it made while being performed became almost inaudible.

During the Chunin Ninja Exams in the original story, Might Guy had said that Chidori was created for assassination. But both Chidori and Chidori were usually used to thrust forward.

It wasn't until Yamanaka Tohru learned Chidori and Chidori that he understood why the technique couldn't be used for assassination: it was simply too loud.

When Chidori was used, it sounded like a thousand birds calling out, just as its name suggested. Chidori had improved on that, but it still wasn't perfect.

By adding Senjutsu Chakra to Chidori, Yamanaka Tohru had made it suitable for assassination.

After about a minute, Yamanaka Tohru's Sage Mode automatically wore off. Just as Sage Fukasaku had said, he was too young and didn't have enough Chakra. Although the Yin Seal replenished the Nature Energy he used up, his own condition wouldn't allow him to maintain Sage Mode for long.

Once he had recovered, Yamanaka Tohru entered Sage Mode again. This time, he didn't use Chidori or activate Lightning Release Chakra Mode. He maintained Sage Mode for less than two minutes.

He tested it again, using Chidori, Lightning Release Chakra Mode, and Chidori Blade while in Sage Mode. It lasted for less than a minute.

After establishing how long he could maintain Sage Mode, Yamanaka Tohru stopped training. He needed to ask Sage Fukasaku about how to fight while in Sage Mode.

The next day, Yamanaka Tohru found Sage Fukasaku, who was training Jiraiya.

Jiraiya still hadn't figured out how to become one with nature. Sage Fukasaku couldn't help him with that, so he could only tell Jiraiya to work it out for himself.

"Tohru, what is it?" Sage Fukasaku had already sensed Yamanaka Tohru's arrival.

"Sensei Fukasaku, I'd like to learn how to fight in Sage Mode." Yamanaka Tohru got straight to the point.

"Tohru, didn't I tell you? You can't enter Sage Mode. What are you—"

Before Sage Fukasaku could finish, Yamanaka Tohru entered Sage Mode. Sage Fukasaku and Jiraiya stared at him, dumbfounded.

Sage Fukasaku was stunned by how well Yamanaka Tohru had mastered Sage Mode. He had been certain Yamanaka Tohru couldn't enter it, yet somehow he had succeeded—and his Sage Mode was far more complete than Jiraiya's.

Only then did Sage Fukasaku notice the Nature Energy flowing from the Yin Seal on Yamanaka Tohru's forehead.

"Tohru, are you absorbing the Nature Energy from that Sealing Jutsu?"

Yamanaka Tohru didn't tell Sage Fukasaku about the special Nature Energy inside him. So when Sage Fukasaku noticed the Nature Energy flowing from the Yin Seal, he assumed that Yamanaka Tohru controlled the flow into his body by means of the Sealing Jutsu.

Yamanaka Tohru nodded without saying a word.

"Kid, how long can you maintain Sage Mode?" Jiraiya asked.

"Two minutes if I don't use any jutsu."

"Tohru, you don't have enough Chakra. You'd better use Sage Mode sparingly for now. Wait until you're older and have more Chakra before using it."

"Yes, Sage Fukasaku."

"But Tohru really is a genius. He actually came up with a way to control the flow of Nature Energy into his body," Sage Fukasaku said admiringly.

"Boss, you're wrong. It's because a genius like me helped this kid rewrite the Sealing Jutsu formula that he can enter Sage Mode." Jiraiya finished with a loud, smug laugh.

"Jiraiya, you can't even enter Sage Mode on your own. Why don't you get back to training?"

"Yes, Boss." Jiraiya immediately backed down at the stern look on Sage Fukasaku's face.

"Tohru, I'll teach you Taijutsu for Sage Mode."

"Yes. Thank you, Sage Fukasaku!"

The author's note: I looked into it specifically. Creation Rebirth, used by Tsunade and Sakura, is the result of releasing all the Chakra stored in the Hundred Healings Mark. The release of the Hundred Healings Mark can be controlled.