It wasn't strange that Neji would ask that. If you picked anyone in the current shinobi world other than Uchiha Chizumi, they'd probably be just as stunned after hearing Hiashi's words.
After all, in the minds of people in the shinobi world, the shinobi world itself was the whole world.
"It's exactly what you're thinking. Beyond this land—up in the sky—is what we call 'outside the shinobi world.'"
Since Hiashi had already decided to reveal the secret that only the head of the main family was supposed to know, there was no point in dragging it out.
"According to the ancient records passed down in the Hyuga clan, the Hyuga were not originally a native clan of the shinobi world. We came from the moon."
"And on the moon, there is another branch of people distantly related to our Hyuga clan."
"Or rather… our Hyuga clan should really be called the Otsutsuki clan."
"You remember Hinata's third birthday, don't you?"
"On that day, those clansmen from the moon came to see her."
As if that revelation still wasn't shocking enough, Hiashi went even further and told Neji, in full detail, that Otsutsuki Toneri had come to Earth when Hinata was three years old.
"They can come to the shinobi world…"
Neji was beginning to understand Hiashi's fear. If every single Hyuga ended up branded with the Caged Bird Seal, then the branch on the moon would likely be able to completely control the life and death of the Hyuga clan.
"Not just come to the shinobi world. The Hyuga clan's Caged Bird Curse Mark was developed specifically to guard against them."
"According to our clan records, a few hundred years ago, the branch living on the moon slaughtered our Hyuga clan on a massive scale. In the end, our ancestors had no choice but to create the Caged Bird Curse Mark."
"That way, even if the moon branch ever tried to massacre the Hyuga clan again, the main family could activate the Caged Bird Seal and ensure they gained nothing."
Hiashi let out a cold laugh. Did Neji really think the Otsutsuki on the moon created the giant Tenseigan entirely on their own?
That thing had always contained a part of the Hyuga clan. Or more accurately, the overwhelming majority of that giant Tenseigan on the moon had been built from Hyuga eyes.
"But if they're our clansmen, why would they massacre us?"
Neji couldn't understand. If the Hyuga clan and the moon branch shared the same ancestors, he couldn't imagine what reason there could be for them to target the Hyuga like that.
"Because of the Byakugan."
"Or rather, because of the Byakugan's next evolution."
"The Hyuga clan's Byakugan is ranked alongside the Uchiha clan's Sharingan—not because we boast about it, but because it's simply true."
"You already know that for the Uchiha clan's Sharingan to evolve into the Mangekyo Sharingan, it requires an extreme emotional shock. So what do you think the Byakugan needs in order to evolve?"
Now that Hiashi had chosen to reveal the deepest secret of the Hyuga clan, he naturally wanted Neji to properly face what it meant to be Hyuga.
At the very least, he wanted Neji to understand one thing clearly:
The Hyuga clan had never been inferior to the Uchiha clan.
Not in the past. Not now. And not in the future.
"It requires purity. Absolute, unparalleled purity."
Without waiting for Neji to think of an answer, Hiashi gave it himself.
"The Uchiha clan's Mangekyo Sharingan requires extreme emotional stimulation. But for the Hyuga clan's Byakugan to evolve further, what it needs is the purest bloodline—the purest Byakugan."
"And in your generation, Hinata's Byakugan is the purest. So pure that the Otsutsuki on the moon called her the Byakugan Princess."
"In other words, Hinata has the potential to awaken a level of eye beyond the Byakugan."
"And if Hinata really were to awaken that eye, then in the entire shinobi world—no, perhaps only the legendary Sage of Six Paths would possess power equal to hers."
"And that is the real reason why, even knowing Hinata's personality wasn't suited for it, I still delayed putting the Caged Bird Seal on her."
Hiashi spoke slowly.
By the inheritance rules of the main family, even he, as clan head, should have left only one child as a main family member. Back then, he had always used Hanabi's young age as an excuse.
But only Hiashi himself knew what kind of potential Hinata actually possessed.
Unfortunately, as a father, he had been far too rigid. He wouldn't even let his own daughter eat her fill. Otherwise, with Hinata being recognized by the moon's Otsutsuki as the Byakugan Princess, she might really have awakened the Tenseigan.
Even if her eyes had only begun to show the faintest trace of blue, that still would have meant they were evolving in the direction of the Tenseigan.
Then again, it was also possible that Hiashi had deliberately restricted Hinata's food intake. After all, if Hinata had gradually awakened the Tenseigan, what would happen if the Otsutsuki on the moon came to take her away?
"Under normal circumstances, the only way for the Byakugan to evolve is through natural awakening."
"But a few hundred years ago, the Otsutsuki on the moon came up with another method."
"They gathered huge numbers of Byakugan—thousands, even tens of thousands—and fused them all together. With enough of them, they believed a higher form of the Byakugan would inevitably be born."
"And that eye would stand on the same level as the eyes of the legendary Sage of Six Paths. It would possess the power to dominate the shinobi world."
By this point, Hiashi had more or less told Neji all the major secrets of the Hyuga clan.
As for what Neji would choose to do with that knowledge…
"An eye… with the power to rule the shinobi world…"
Neji looked stunned. No matter what, he had never imagined that the Hyuga clan's Byakugan could continue evolving—let alone that if it did, it would gain the power to dominate the entire shinobi world.
"A few hundred years ago… did the Otsutsuki on the moon succeed?"
Neji took a deep breath. By now, he understood why the Hyuga clan had clung so desperately to the Caged Bird Seal.
If the moon branch of the Otsutsuki had once descended to the shinobi world and slaughtered the Hyuga clan, and if the Otsutsuki had also come down again when Hinata was three, then that meant one thing:
If the Caged Bird Seal were ever removed entirely, that distant Hyuga branch on the moon could very well launch another massacre against the Hyuga clan.
"They failed."
"If they had succeeded, there would be no us—and no shinobi world as it exists today."
"The Otsutsuki on the moon bear the duty of purging the shinobi world. If the shinobi world becomes corrupted, they are supposed to use the Tenseigan to cleanse it."
"You and I both know exactly what the shinobi world is like. If the Otsutsuki on the moon still haven't launched their attack, it certainly isn't because they're benevolent."
"The only explanation is that their Tenseigan plan was never truly completed."