When Gamamaru saw Sasuke, he was taken aback and all his sleepiness immediately disappeared. He seems to have seen something in Sasuke, and exclaimed in surprise, "Indra."
Gamamaru has lived for over a millennium, therefore, the moment he saw Uchiha Sasuke, he immediately recognized that Sasuke is the current reincarnation of Ōtsutsuki Indra.
At the same time, Gamamaru also saw vague fragments of the future in which Sasuke would play an important role.
Many people are aware of the fact that Gamamaru can foresee the future, time and time again, he has demonstrated this ability. Using his ability to foresee the future, Gamamaru must have known that only the Ōtsutsuki brothers Hagoromo and Hamura–who inherited their Chakra from Kaguya–could resist her, so he cleverly approached the two brothers and confused them to rebel.
At the moment when Hagoromo was going to fight Kaguya, he handed over a special seal tag to Hagoromo. Again, Gamamaru must have known that Hamura would die at the hands of Hagoromo so he gave a seal tag that can resurrect the dead.
Gamamaru cleverly did not point out this to Hagoromo, probably because he foresaw the future, and understood that it was necessary for Hagoromo to kill his brother in order to awaken the Rinnegan.
Later, Gamamaru foresaw the result of the test that Hagoromo gave to his children Indra and Asura while deciding his heir.
And finally, Gamamaru also led Jiraiya on the path of searching for the 'Son of Prophecy'.
However, the problem is, for quite a few years now, Gamamaru has stopped seeing anything related to the future, that is, up until now.
Therefore, when Jiraiya saw the change in Gamamaru, he immediately got up and asked, "Lord Gamamaru… what happened? Did you see something?"
Being aware of the concept of 'cause and effect' Gamamaru chose not to reveal anything and changed the topic with a small laugh, "Oh no… nothing… I was just surprised at the excellence of these children." Then he turned towards Fukasaku, and instructed him, "Take a test of these children."
Everyone was confused by Gamamaru's unnatural behavior, however, no one said anything about it and followed Gamamaru's instructions.
Jiraiya and Fukasaku nodded lightly then led the four children to the Sacred Oil Fountain.
…
Looking at the four children, Elder Fukasaku carefully thought about the words Gamamaru said to him in private, then said, "All right children… I will be teaching you the Special Senjutsu of Mount Myōboku. Those of you who can successfully cultivate Senjutsu will pass the test, understand?"
"Senjutsu?" Hearing Fukasaku's words, the four children were surprised and got excited. Sasuke and Neji were more eager to learn Senjutsu.
Noting the kid's excitement, Jiraiya quickly said, "Don't be so excited, Senjutsu is not that easy to master!"
Sasuke said in a dissatisfied tone, "If Naruto can learn it, then I can too!"
Jiraiya smiled and shook his head. Since Naruto has mastered Senjutsu, people have started to misunderstand it, now every ten-year-old kid thinks that he or she can learn Senjutsu.
What they don't seem to understand is that Naruto has mastered Senjutsu under special circumstances as such he is an exceptional case, and not everyone can be as special as Naruto in this regard.
Let alone others, Jiraiya, and Shisui haven't completely mastered Senjutsu. Even now both of them need assistance while using the Senjutsu mode. Perhaps the only known person to have perfectly mastered the Senjutsu Mode is Shodaime Hokage of Konoha, Senju Hashirama.
Coming back to the topic, as Elder Fukasaku led everyone to the training area at Sacred Oil Fountain, the children noted the giant toad-shaped rock statues, and asked curiously, "Fukasaku-sama, why are there so many statues here?"
"Huh… these… they are not simple statues… they are all people who failed to master Senjutsu." Said Elder Fukasaku, and added with a solemn tone, "When training the Senjutsu Mode of Mount Myōboku, the practitioner will gain the features of a toad… in this process, once the natural energy inside the body gets out of control, the practitioner's entire body will turn into a toad and then petrify into a stone statue."
"What?" All four children were horrified upon learning the truth.
At this time, Jiraiya said with a smile, "Mastering Senjutsu is not as easy as you all are assuming it to be, don't think that just because Naruto mastered it, you lot will master it as well, Naruto is an exceptional case!"
Elder Fukasaku said, "The reason these people became statues is that they were too greedy and rash for power. You people don't have to worry too much, even if all of you fail to master Senjutsu, I can at least ensure that none of you will become a toad statue."
Sasuke breathed a sigh of relief when he heard Elder Fukasaku's words. And quickly asked, "Fukasaku-sama, will we become toad when we use Senjutsu?"
Kiyomi, Neji, and Hinata looked at Fukasaku, none of them wanted to become a toad.
Elder Fukasaku naturally understood the children's dilemma, and said with a smile, "Don't worry… when training the Senjutsu Mode of Mount Myōboku, although the user gains toad features, however, they don't become toads. In the future, when your mastery increases, the toad features will become less and less visible and totally disappear."
This also means that the more secondary features appear in a person's body, the less his mastery in Senjutsu and vice versa.
Senju Hashirama had the least amount of features on his body when he used the Senjutsu Mode, except for a few lines under his eyes, there were no changes. Naruto's mastery was even better compared to the Shodaime Hokage. When he entered the Senjutsu Mode, except for the change in his pupil, there was no other change.
In comparison to Naruto and Hashirama, Jiraiya and Shisui's mastery of Senjutsu is obviously inferior.
Well putting that aside, Fukasaku's words relieved the four children and they were ready to try.
With that, Elder Fukasaku took some toad oil from the fountain and rubbed a few drops on the arms of the four children, while instructing, "This is special toad oil, it will help you sense the natural energy spread in the heaven and earth, start concentrating, and try to sense the Natural Energy."
The four children nodded, and under the guidance of Elder Fukasaku, they tried to sense the Natural Energy dispersed in heaven and earth.
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Read up to Chapter - 1020 on P.a.t.r.e.o.n Page: p-atreon.com/Milta_translations