After being forcefully reincarnated, Yorugami was sent to his own World (Narutoverse) near a human village. Luckily for him, he was reincarnated as a child.
But after his banishment, all of the Darkness that he had held back for centuries, without any other God taking the Duty of Balance, spread out around the whole universes with a tremendous tainting effect.
Because of the influence many humans began to attack each other out of fear, anger, hate, jealousy, resentment, bitterness, worry, suspicion, anxiety, mistrust, grudge and soo on. And because of the happening fights, conflicts and strife, trough the whole worlds and universes began to happen World Wars. Because of the Wars, countless humans had lost their lives.
The ones who had died with a grudge, was either brought to live as Monster or Demon. Until the whole worlds´s living beings began to separate in to more than five different species. Monsters, Demons, Supernatural Beings, Mythical Beings, Tailed Beasts and so on began to come into existence.
Because of the Wars and his inhuman abilities, reincarnated Yorugami no Mikoto, now named Mangetsu was seen as a monster. Because of his treatment, Mangetsu continued to live in the mountains all alone at the outskirts of the village.
One night during his stroll around the mountain, when Mangetsu came out a clearing and looked up, he saw something falling from the sky slowly. As the thing neared to the ground before him, Mangetsu grasped the floating and glowing white piece. Without knowing what it was really, as he was in trance, after lifting the piece to his mouth, Mangetsu ate it.
As he consumed the piece, because of the caused effect, he learned that this piece actually belonged to the newly created Onmyō-Tsuki (Yin-Yang Moon).
The Onmyō-Tsuki would come in creation once a Millennium, when the Hikari no Yō-Tsuki (The Yang Moon of Light) and Yami no In-Tsuki (The Yin Moon of Darkness) merges together. These two Moons are actually celestial power sources that after appearing; the Yō-Tsuki would grant power to the ones who has light inside their heart in need, which the In-Tsuki would do the same but to the ones who has darkness in their heart.
Because of eating the Piece of the Onmyō-Tsuki, not only Mangetsu was connected to the both Moons directly, but also he became a Hybrid Tailed Beast of a Black Fox and Black Dragon.
After coming out of age, even he hadn't done anything against them the villagers attacked Mangetsu in hopes that he would get far away, as there wasn't any other choice, he flied from the Island he lived until that time.
Couple of centuries later, during his travels Mangetsu met a Fairy Princess named Seiju Megumi, guarding the Fountain of Youth that was on top of the Seiju. The more he was with her the more Mangetsu fallen in love with Megumi, which he stayed with her over decades. Unfortunately, both of them were attacked by a giant demon that Mangetsu never saw before.
Thinking he had won after ripping its heart, right after he turned to face Megumi, both of them were wounded fatally from the not yet-death giant demon´s claw.
As Megumi forced him drinking some water of the Fountain of Youth with her mouth, Mangetsu´s sealed regenerative ability was unsealed. After his fatal wound was completely healed without a scar, Mangetsu attacked the giant demon with his own claws in rage and literally ripped the giant demon to pieces.
A while later of being done with his revenge, Mangetsu took Megumi to his embrace, which she gave him a new seed of the Seiju (Holy Tree) that was burned to Mangetsu. Afterwards of giving the seed, Megumi confessed to Mangetsu about her love to him.
And just as Mangetsu was telling her that he would make her his, in desperate tone, Megumi passed away in his arms. As she had died, Mangetsu whispered to himself sorrowfully that she should at least let him finish.
Some years had passed and after finding an untouched wasteland, Mangetsu planted the seed of the Seiju there, however since he didn't have water with him, to irrigate the seed, he cut his wrist open with his claw and allowed a great deal of his Kokketsu flowing out over the seed.
After determining it was enough, Mangetsu began to heal his wound. But as he was healing, he didn't noticed that the seed grew taller than him into a still growing tree. As he noticed it and decided that his job was done, Mangetsu flied off somewhere else away to continue his travel and adventures.
The more older he had got, the more worse the Wars began to happen with many sacrifices. During his travels, Mangetsu befriended a lot of beings that he came to trust completely. As he befriended and saved many beings, Mangetsu decided to create a Clan on his own. As means to strengthen their bonds and protecting his now precious people, Mangetsu shared his Kokketsu with his Comrades. After a two staged ritual, the Hokori Takaki Kurotsuki Ichizoku, Kurotsuki Mangetsu as their Ancestor was created.
However even after thousand years, the Kurotsuki Clan was still unknown to the Zenkai, as Mangetsu knew they would be hunted because of their blood, if their existences where to be know trough the world. As a result, Mangetsu was living with his Clan in utter secret in a island (Yatsuki-jima) that he had created.
Nonetheless their peace and luck was cut short. A jealous clan-member that envied the stepsons of Mangetsu; Kurotsuki Yasuna, Hibari, Hiruto and Kazuya, after having enough betrayed the clan.
The traitor didn´t only betrayed the Clan but had also done something that lead to the Kurotsuki Clan´s slow extinction.
The Kurotsuki Clan was one of the Clans of Tailed Beasts, that consisted of two Main Branches. The first, Kuroko Branch and the second, Kokuryū Branch. The clan members were born with a Kekkei Tōta; Shiketsumyaku (Dead Blood Pulse) and with Jiko Chiryu-Nōryoku (Self Healing Ability). Shiketsumyaku allowed to it´s user, complete control over their and if trained enough, enemies blood and blood flow. The users could create near indestructible weapons made from their blood and if mastered enough, an armor that envelopes their own body for guarding purposes. If mastered ultimately, complete control of their own body, even if their body were to be paralyzed, they could still move while controlling their body at will with their Kokketsu. Even being an overpowered Power Source, Kokketsu has only one weakness the Junketsu or with another name, Human Blood.
In the past (even now) existed 3 types of Blood: Junketsu, Maketsu (Demon Blood) and Kokketsu (Norowareta-Chi). Being a pure blood from humans, the Junketsu would purify the Kokketsu into a normal red colored blood, if even one drop of Junketsu were to enter inside the Kokketsu-users body, from a open wound. It would effect them as an lethal poison capable of paralyzing the users body and leading to their death, if not removed on right time. The same would happen the opposite way, as the Kokketsu is capable of turning any type liquid into new Kokketsu, hence the cursing.
The traitor didn't only let the Kurotsuki Clan´s existence be known to the whole world, he had also told the abilities of Kokketsu and only existing weakness to the most strongest warring countries.
Seven of these warring countries, after creating an alliance, sent 150000 forces to the Yatsuki-jima to capture many Kokketsu-users as much as they could.
Because of his spies around the whole world, Mangetsu learned about the coming raid one day beforehand. But rather than ordering his clan, which had became a big village, to get ready for the raid, he ordered to the whole clan to leave Yatsuki-jima and to Live.
When all of them proven themselves to be royally stubborn to leave him, without giving them a chance, Mangetsu transported all of his clan-members from their home and forced them to leave their beloved Ancestor behind to face the coming raiders.
After fighting three days straight and killing every 150000 raiders, to catch his breath Mangetsu leaned down to a boulder and began to succumb to his lethal wounds, that was caused from Junketsu coated weapons.
Afterwards of gazing at the night sky, Mangetsu passed away while being proud that he could protect his clan for a time being.
Before ordering his Clan to leave, during the meeting he had ordered to gather he told to the Elders; if he were to die, Yasuna will be the Second Clan-head, as he is the eldest heir. And he would reincarnate as an white haired baby.
Trough the coming years, many other warring countries hunted the Kokketsu-users down, which lead them to separate and scatter around the whole world as a means to protect themselves and each other.