Yangkura let out a noise that was halfway between a sigh and a growl. "Is it so important that we have to interrupt?"
"I don't know, it might be?" Naruto said, still confused. "I mean, on one hand, it's your history and I want to know more, and.. it's ancient history and that might have some clues about this whole thing with Madara and the Juubi, so... I guess?"
The two halves of the Kyuubi shared a glance. After a moment, Yinkura nodded.
"Alright, fine." Yangkura said, growling slightly. "Pay attention, because I will not be saying any of this again."
Naruto sat up straighter, giving the Kyuubi his full and undivided attention.
"Many, many years ago, during an era of war, there was a tree." Yangkura stated, his eyes drifting half-closed. "That tree was called the Shinju, the God Tree. This tree, as its name implies, was sacred; every thousand years, this tree would bear a fruit, which was known as the Chakra Fruit."
"A woman by the name of Kaguya Ōtsutsuki claimed that fruit for herself, and in doing so, became the first being on this world to wield the power of Chakra." Yinkura continued for him. "With that power, she seized control over the world, ending the wars, and became known as the 'Rabbit Goddess'. She gave birth to two beings, the second and third people to wield Chakra. Their names were Hagoromo and Hamura. The latter has faded from history, but you know the former as the 'Sage of Six Paths'."
Naruto started, surprised at that.
"Eventually, she went mad with power, and started ruling through fear." Yangkura stated. "She was subsequently called a Demon, instead of a god."
Naruto frowned.
"Eventually, a beast appeared." Yinkura continued, not giving him much of an opportunity to think on it. "That beast was, in fact, the incarnation of the God Tree, which, angered by the spread of Chakra, had come to reclaim it."
"It was the Juubi, wasn't it?" Naruto asked, though it wasn't really a question.
Yangkura nodded. "Hagoromo and Hamura fought against the Juubi, and eventually claimed victory. Hagoromo sealed it within himself, locking it away so that it could do no harm."
"He became a Jinchuuriki?"
"In effect." Yangkura agreed. "Though it was by his own choice."
"What happened afterwards?"
"Life." Yangkura stated. "They travelled the world, learned its ways, and imparted their own wisdom. Eventually, Hagoromo would even share the power he possessed with others, teaching the art of Ninshū, and passing along his ideals of peace and cooperation as he did."
"Ninshū?" Naruto asked.
"It was the pure form of the Sage's teachings before it was bastardized into Ninjutsu." Yangkura answered.
"The idea behind it was that one would use their Chakra to connect their own spiritual energies with another person's spiritual energies, allowing them to understand each other at the deepest level." Yinkura explained a bit more. "Of course, you Humans are incredibly ungrateful, so instead of doing that and achieving peace and prosperity, you instead started linking your physical and spiritual energies, amassed personal power, and warred over petty things like stolen jewelry and insults."
Naruto got the impression that the Kyuubi had understated the reasons.
"Regardless, the Sage of Six Paths wandered the world for over a decade, until he eventually fell in love and had two children of his own."
"The Sage had descendents?"
"More than you realize." Yinkura answered. "His entire bloodline was quite prosperous, even if it was culled a few times over the years."
"His children were named Indra and Asura, the older and younger, respectively."
"The same guys you mentioned before?" Naruto frowned. "I... had the impression they weren't friends?"
"In the beginning, Indra and Asura were two entirely normal children. Brothers, indeed. However, when Hagoromo began to teach them Ninshū, Indra was found to possess incredible aptitutde, while Asura did not. Indra, through his talent, never needed to rely on others, and was quick to grasp any concept and overcome any challenge he was presented with. As a result, Indra became distant, only ever relying on himself. Asura, however, frequently relied on others, and so came to value and connect with everybody around him. Indra's isolation and growing arrogance contrasted with Asura's cooperation and compassion. Things eventually came to a head when the Sage of Six Paths declared Asura his successor, sparking jealousy in Indra, and causing them to come into conflict."
"They fought. Asura won." Yinkura noted. "Indra hated him for it. It was the start of a generations long feud between them and their descendents, who would eventually come to be known as the Uchiha clan on the part of Indra's descendents, and the Senju clan on the part of Asura's."
Naruto's eyes widened. "The Uchiha and Senju descend from the Sage?"
"You yourself do, actually." Yinkura stated. "The Uzumaki clan also descends from Asura, so Hagoromo would also be somewhere in your family tree."
"That's-" Naruto held up a hand, before stopping, a thoughtful look crossing his face. "Actually, considering how long ago that was, that's not too surprising. The real question would be who he isn't related to, in this day and age."
Yangkura grunted. "Either way, it was so long ago that it basically doesn't matter."
Naruto nodded. "Wait, what happened to the Juubi, then? How did it get from the Sage to... wherever it was sealed?"
"That came afterwards, actually." Yangkura answered. "Before the conflict between Indra and Asura, but after they had grown into their natures. Hagoromo was inspired by Asura, and came up with idea of splitting the Juubi's chakra into multiple pieces, further separating its power and reducing the chance it would ever be able to come back."
"He settled on nine, in the end." Yinkura added.
Naruto blinked. "Nine..? Wait, you don't mean-"
"Those nine pieces were us, of course." Yangkura laughed, delighting in breaking Naruto's brain. "We Bijuu. That was our beginning, our birth; Nine pieces of the Juubi, created by Hagoromo Ōtsutsuki, another set of children to go with his two sons. The Sage of Six Paths is our father."