Natural energy was a remarkable thing. It had existed in the Shinobi World before chakra appeared, and perhaps it could also be called the life energy of a planet. At the very least, whether a planet could nurture life depended on whether it had natural energy.
The Ōtsutsuki Clan also had to choose planets containing life energy to plant their God Trees, or the trees could not grow.
After Ichikishimahime helped inject natural energy into Karn with her snake fangs, he spontaneously sensed the abundant natural energy around him through the natural energy inside his body. Although the wound on his neck quickly healed under the effects of the Extremis Virus, he could still clearly sense the natural energy outside his body.
In an instant, a large amount of natural energy surged toward Karn. Once it entered his body, he controlled it to produce senjutsu chakra. But as more and more natural energy poured in, he began to feel he was losing control before even a minute had passed.
"Too reckless. A beginner should absorb natural energy slowly. That much natural energy is already beyond what your chakra can control."
Ichikishimahime spoke softly and prepared to step forward and bite him again, drawing all the excess natural energy out of Karn's body. This was what Ryūchi Cave meant by guaranteed success. The Three Divine Hime could take in and extract natural energy, allowing them to help practitioners perfectly control the natural energy inside their bodies.
No matter how little chakra someone had, Ryūchi Cave could help them succeed in their training. However, they almost never did so, because none of the Three Divine Hime wanted a ninja to successfully master Sage Mode.
Karn was an exception. He and Orochimaru could bring Ryūchi Cave considerable benefits.
Hiss!
Just as Ichikishimahime was