Inner Ice Release

After learning about Hozuki Mangetsu's ability to fuse Ice Release chakra, Uesugi Shinji continued his own training.

To Uesugi Shinji, Hozuki Mangetsu was merely a condition for cooperating with Terumi Mei. He had no intention of devoting too much effort to him.

More importantly, he had made a major discovery during his recent clash with Namikaze Minato. It had given him a new direction after his growth in strength had hit a bottleneck.

The key to this discovery was none other than Namikaze Minato's Summoning Beast, Gamabunta!

As a core member of Mount Myoboku, one of the Three Great Sage Regions, Gamabunta had known how to use Natural Energy in battle since birth. This was the biggest difference between the Ninja Beasts of the Three Great Sage Regions and other Summoning Beasts.

Gamabunta constantly maintained a large amount of Natural Energy within his body. When using ninjutsu, he also fused Natural Energy with chakra, allowing his techniques to unleash much greater power.

However, Natural Energy was colorless and formless, so ordinary ninjas could not detect it at all. The methods for using it had thus become a closely guarded secret of the Three Great Sage Regions.

But Uesugi Shinji had the Light Brain, and he had actually discovered the Natural Energy that was ubiquitous in the air long ago.

The air in the Shinobi World contained oxygen, nitrogen, Natural Energy, and various other substances. Uesugi Shinji had never paid attention to Natural Energy before, not until he saw Gamabunta absorb it from the air to replenish himself and then fuse it with chakra to perform powerful ninjutsu.

This discovery filled Uesugi Shinji with excitement. During the time he had spent guiding Hozuki Mangetsu's Ice Release training, he had also been experimenting with Natural Energy—and he was now just one step away from success!

Standing on the clear, still surface of a lake, Uesugi Shinji closed his eyes and sensed the Natural Energy around him, slowly drawing it into his body.

He did not know that the substance he was absorbing was called "Natural Energy," nor did he realize that, according to the traditions of the Three Great Sage Regions, his training was known as "Senjutsu."

The first hurdle in Senjutsu training was sensing the existence of Natural Energy. More than nine out of ten ninjas who had a chance to learn Senjutsu never made it past this hurdle.

But not long after arriving in the Shinobi World, Uesugi Shinji had passively detected the Natural Energy in the air through the Light Brain. This first hurdle simply did not exist for him.

The second hurdle was maintaining a balance between chakra and Natural Energy. Most practitioners who made it past the first hurdle died trying to overcome this one.

Senjutsu training was extremely dangerous. If a practitioner failed to maintain the balance between chakra and Natural Energy, allowing the Natural Energy in their body to exceed their own chakra, it would erode their body and trigger a series of harmful changes.

The effects varied depending on the surrounding environment and the practitioner's chakra nature. For instance, practitioners at Mount Myoboku were petrified when their bodies were eroded by Natural Energy.

At Shikkotsu Forest, absorbing too much Natural Energy would turn the body into deadwood.

Training in Senjutsu at Ryūchi Cave was the most dangerous of all. If Natural Energy went out of control, the body would rapidly decay. The snakes of Ryūchi Cave would not help practitioners who failed—instead, they would swarm over and devour them.

(Note: The effects of Natural Energy erosion at Shikkotsu Forest and Ryūchi Cave are the author's invention.)

Because Natural Energy was so difficult to control and so dangerous, the Three Great Sage Regions required ninjas to have a sufficiently large chakra reserve before they could train in Senjutsu.

The more chakra a ninja had, the more Natural Energy their body could withstand. This made it easier to balance the two kinds of energy, naturally reducing the difficulty and danger of training.

Although Uesugi Shinji did not have much chakra, this second hurdle was no challenge for him either.

With the Light Brain's help, he could precisely control the balance between the chakra and Natural Energy in his body. In general, the principle was much the same as when he had fused Wind and Water chakra to create Ice Release chakra.

Uesugi Shinji had now finished absorbing Natural Energy. The Natural Energy and chakra in his body had reached a perfect balance, and his body began to change.

His formerly jet-black hair and eyebrows gradually turned icy white. A diamond-shaped mark, like a crystal of ice, appeared between his eyebrows, and the lake within a radius of about three meters beneath his feet froze under the influence of his Ice Release chakra.

This was Uesugi Shinji's own Sage Mode, and he called it "Inner Ice Release"!

(Note: In Japanese, "omote" and "ura" are used to describe appearances and reality, as well as light and darkness.)

If a member of one of the Three Great Sage Regions had been here, they would have been astonished to discover that Uesugi Shinji's Sage Mode aura was steady, and that he did not rely on any Summoning Beast capable of controlling Natural Energy to maintain it. This was the final stage of Sage Mode—Perfect Sage Mode.

Uesugi Shinji slowly opened his eyes. His pupils had also turned the color of ice crystals. Even looking into them seemed to send a chill through the air.

He swiftly formed Hand Seals, and a large-scale Ice Release technique was ready in an instant.

"Inner Ice Release: Ice River."

A ring of white light spread out from the lake beneath his feet. In the blink of an eye, the entire lake froze over. Viewed from above, it looked like an exceptionally smooth mirror.

Seeing the result of the technique, Uesugi Shinji's eyes flashed with satisfaction.

After fusing with Natural Energy, the power of his ninjutsu had increased dramatically.

In his normal state, it would take at least five seconds to freeze the entire lake with this technique. The temperature and strength of the ice would also be nowhere near what they were now.

In addition, Uesugi Shinji could clearly feel that his body was in far better condition than usual. It was obvious that "Inner Ice Release" not only increased the power of his ninjutsu but also strengthened his Taijutsu.

"I really have to thank the Yellow Flash. If not for his Summoning Beast, I might have overlooked this ubiquitous energy!"

After mastering "Inner Ice Release," Uesugi Shinji did not feel satisfied. Instead, he became even more eager to complete the Sealing Jutsu he had been researching: the "Outer Path Jade."

Although "Inner Ice Release" was powerful, it could not solve his shortage of chakra. His stamina in battle remained a major weakness.

If he could complete the "Outer Path Jade" Sealing Jutsu as well, Uesugi Shinji believed that he would be among the very strongest in the Shinobi World. Perhaps he might even reach the level of Senju Hashirama and Uchiha Madara, the legends of the past.

"Next, I have to find a chance to get my hands on a Tailed Beast. No, just a part of one will be enough!"