In Tsuchigumo Village,
Sarutobi Hiruzen sat cross-legged in the guest room,
looking at the strange black, round substance rooted in the skin of his exposed arm,
with lines extending from it like a spiderweb, crawling across his skin.
"'Fury of the Heavens'..."
"I see..."
Sarutobi Hiruzen smiled.
"The one who developed this forbidden technique was quite clever."
"They thought to use a substance preserved from their own cells to parasitize someone else's body..."
"and thereby pass down this powerful Senjutsu ability to a certain extent."
It hadn't taken long for the Great Elder to pass the Fury of the Heavens on to him.
Sarutobi Hiruzen had successfully acquired this forbidden technique.
He had also studied it and learned how Fury of the Heavens worked.
"Every so often, a genius will awaken Senjutsu abilities or learn Senjutsu later in life..."
"But clearly, this power is difficult to pass down reliably."
"So the one who developed Fury of the Heavens came up with the idea of altering their Senjutsu cells into a substance capable of parasitizing the human body."
"Thus, they could pass down Senjutsu abilities to a certain extent."
"And greatly lower the requirements for using Senjutsu..."
Sarutobi Hiruzen narrowed his eyes.
"Still, this inherited Senjutsu ability is difficult to control. It can only be used by releasing it all at once."
"Of course, inheriting Fury of the Heavens isn't entirely without requirements..."
"To move a thousand pounds with four ounces, you still need those four ounces."
"You need at least as much Chakra as an above-average Jonin to use Fury of the Heavens."
Of course, for Sarutobi Hiruzen, that was hardly a hurdle.
"Although Fury of the Heavens needs to store up power, and its activation isn't subtle, it can still serve as a significant strategic deterrent in certain situations..."