The White Snake Sage bared two enormous fangs and pressed them against Fugaku's body, sending a surge of Natural Energy into him.
That was one difference between Ryūchi Cave and Mount Myoboku. On Mount Myoboku, trainees coated themselves in Toad Oil and slowly learned to sense Natural Energy. The risk was much lower.
Ryūchi Cave was far more direct. The first trial alone eliminated ninety-nine percent of candidates. When an ordinary Ninja first came into contact with Natural Energy, their body mutated, then slowly turned to stone.
That was why the people who came to Ryūchi Cave to learn Sage Mode were reckless enough to gamble with their lives.
At least, in the history Fugaku knew, after the Shinobi World adopted the one-country, one-village system, only Kabuto Yakushi had managed to learn Sage Mode—and his version was imperfect.
Natural Energy flowed through the White Snake Sage's fangs into Fugaku. He sat cross-legged and carefully sensed it.
The energy was stronger than ordinary Chakra, and far more violent, but his body showed none of the supposed mutations.
Perhaps it had something to do with his constitution. The Uchiha were said to have inherited the Sage of Six Paths' Sage Eyes, while the Senju had inherited his Sage Body.
Yin-Yang power was merging within Fugaku, improving his innate abilities and gradually bringing his body closer to that of the Sage of Six Paths.
The Rinnegan was not merely a mutation of the eyes. The body changed as well, and the Rinnegan could emerge only when the body met certain conditions.
Otherwise, its bearer would end up like Nagato, expending vast amounts of Chakra and even life force every time he used its powers, until he was drained to a husk.
The Sage of Six Paths had learned Sage Mode in an extremely