Akihara Kagura believed there was nothing wrong with the history he compiled.
All the characters that should appear in the history of the Ninja World have appeared, even the drama of the Divine Tree Ten-tails was included, and he even crafted a credible identity for Black Zetsu.
Who is Otsutsuki Kaguya?
Where did this insignificant name come from!
Who is the Six Paths Sage?
Everyone in the Ninja World knows what kind of figure the Six Paths Sage is!
Akihara Kagura diligently helped Black Zetsu fabricate a respectable identity, the will split from the Six Paths Sage is much stronger than that of Otsutsuki Kaguya…
Because everyone has heard of the name of the Six Paths Sage, they would certainly have more respect for Black Zetsu, the will split from the Six Paths Sage, especially since Akihara Kagura plans to give it a positive spin…
[The appearance of Black Zetsu was an accident.]
[Since Otsutsuki Hagoromo, the Six Paths Sage, was a mere mortal, eventually he would be tortured by aging, sickness, and death. Upon seeing his younger daughter Otsutsuki Kaguya devour the Divine Tree Ten-tails and gain infinite life force, the compassion Hagoromo had for all beings was overtaken by the desire for immortality obtained by devouring the Ten-tails…]
[Black Zetsu is the darkness resurrected within Otsutsuki Hagoromo, the Six Paths Sage, it is the deepest embodiment of his desire. It sought the power of the Ten-tails for immortality, to become the ruler of this world. Otsutsuki Hagoromo could not kill it, so he had to split it off to prevent Black Zetsu from polluting his soul…]
[The Chakra of the Divine Tree Ten-tails had long been split into the nine Tailed Beasts scattered across the Ninja World. The younger daughter, Otsutsuki Kaguya, fused with the Ten-tails' body and was sealed within the Moon. Black Zetsu's first goal upon birth was to devise a way to collect all pieces of the Ten-tails to resurrect his younger daughter, Otsutsuki Kaguya, thereby controlling her and obtaining the power of the Ten-tails…]
This is the origin of Black Zetsu.
Akihara Kagura plans to craft Black Zetsu's desire to resurrect the Ten-tails into the narrative that Black Zetsu is seeking immortality for itself, as this better suits the aura of a manipulator behind the scenes.
Otherwise…
Could one say Black Zetsu simply wanted to save someone?
That would be too inconsistent with the identity of a mastermind!
Moreover, this reasoning can withstand scrutiny, as Black Zetsu's objective indeed is to collect the Tailed Beasts to resurrect the Divine Tree Ten-tails, Akihara Kagura merely provided it with a more grandiose excuse…
Though this excuse is false…
Yet it seems more true than the truth itself!
Apart from the identity, everything else is true.
[Black Zetsu's power is not great, but it possesses the Yin-Yang Release left behind by the Six Paths Sage, and has secretly hidden a portion of the Divine Tree's power, allowing Black Zetsu to live eternally, invulnerable to anyone, and enabling it to merge with the Divine Tree Ten-tails' power…]
This is essential!
Indeed, Black Zetsu's strength is not impressive, but it's incredibly difficult to kill!
The fabrication of Black Zetsu's history has been completed. The subsequent compilation needs to combine truths and lies to make the story reasonable.
[Otsutsuki Hagoromo, the Six Paths Sage, to prevent his dark will, Black Zetsu, from reviving the Ten-tails, proactively sealed this part of history on a stone tablet, and then passed this stone tablet to his most talented and wise eldest son, Indra, who possessed the Sharingan…]
[The eldest son, Indra, of Otsutsuki Hagoromo, was naturally intelligent, creating the hand seals used to perform Ninjutsu and inheriting a powerful Sharingan. Otsutsuki Hagoromo hoped that Indra would take on the responsibility of sealing Black Zetsu. To prevent others from discovering the secrets of the stone tablet, Hagoromo left a restriction on the tablet so that only the Sharingan could decipher its contents…]
[However, the second son, Asura, was naturally simple-hearted, so Otsutsuki Hagoromo decided to pass on the Ninja Sect to Asura, hoping he could grow it stronger…]
[However, things changed. Black Zetsu, the will split from Otsutsuki Hagoromo, upon learning of the tablet detailing its origin, quietly altered the content on the stone tablet…]
[Still, Black Zetsu itself didn't possess great strength, so it claimed to be the will manifested from the power boost of Indra, persuading him to acquire the power of the Divine Tree Ten-tails along the path of his younger sister, Otsutsuki Kaguya, leading Indra to attack Asura and Otsutsuki Hagoromo. Indra thus attempted to capture all Tailed Beasts in the Ninja World to resurrect the Divine Tree Ten-tails…]
[Fortunately, the dying Otsutsuki Hagoromo bestowed his power to Asura, who led the Ninja Sect to defeat Indra, resolving the Ninja World's second crisis…]
[During this crisis, Otsutsuki Hagoromo, upon realizing before his death that the stone tablet's content was altered by his own will, Black Zetsu, knew that the undying Black Zetsu would certainly incite chaos in the Ninja World to resurrect the Ten-tails. The Ninja World's future was bound to witness strife due to Black Zetsu's machinations…]
[To correct the wrongs borne from his manifested desires, and to prevent conflict between the descendants of Indra and Asura which could be taken advantage of by Black Zetsu, Otsutsuki Hagoromo decided to write this secret history on the bark of the Divine Tree and passed it to his second son, Asura, hoping future generations in the Ninja World would be vigilant of Black Zetsu…]
Here the story takes a pause.
Because Akihara Kagura wrote it from the perspective of Otsutsuki Hagoromo, the Six Paths Sage, he added a touch of regret and shame for not controlling his desires, which resulted in the creation of the eternal monstrosity that is Black Zetsu, hoping future generations would not lose themselves to power.