Prologue:
In the beginning of time, there were four entities that ruled the Universe – Life, Chaos, Order/Law, and Death. The universe was large and expansive, larger than human imagination could stretch, and yet, empty, dull, and completely lifeless. The entities that ruled got tired of this great lot of nothing, and Life and Order brought forth new entities, demigods – if you will – to keep them entertained. The demigods were the first youkai, and the four great entities created a world upon which they could dwell – it was called Gaia.
Along with the youkai, the entities created a race of humanoids that could live alongside these youkai, even if there was fighting and destruction at times. The entities were amused, and had no idea that they'd just created a civilization that would thrive for countless millennia to come.
They would grow to call themselves humans, and they were a driving force in shaping their new world.
Eventually, Life and Death became primal forces, rather than entities, along with their brothers of Order and Chaos. Humans chose the way they wanted their gods represented, and youkai didn't really believe in a higher power – only that they WERE the higher power. The entities melded into the flow of the universe, becoming one with the machine they'd created.
But it didn't last. Death reemerged in the next thousand years, in the form of a woman. It lived out a humans life, until its powers manifested in its sixteenth year of life. It once more became a conscious force, and sought to reinstate itself as a god. It was not the only one - its former brethren emerged as well, and one in particular – Chaos – would establish for herself a wicked bloodline that would stretch into the present time.
Chaos lived as a human, a human with great destructive potential. She met a man – well, a male dog youkai - whom she believed was the complete embodiment of hatred, and who possessed strong magical talents. They mated, and produced a son whose name would be feared for generations – Aku Taiki, the conqueror of the Eastern Lands. Known simply as Lord Tai, he would work closely with Chaos and Hatred to bring destruction to the world.
Life came to Earth in the form of a woman. Her name was Chiyoko, and she eventually married the Lord of the North, Takenaka Masaru, who fathered the girl that was orphaned at the age of 10 – Takenaka Sakura.
Order/Law came about in the body of a dog youkai who was only ever known as Inu no Taisho. He fathered two sons – a full-blooded dog youkai named Sesshoumaru, via a female dog youkai named Bara, and a hanyou/Halfling named InuYasha, via the fallen noble house of Hayashi's only daughter, Izayoi. Unfortunately, the great Inu no Taisho died of injuries inflicted upon him in the great battle with Ryuukossei, when InuYasha was barely two years old.
Before his death, however, Inu no Taisho had taken an orphaned kitsune child under his care, the girl's father being someone he respected. She, Sakura, lived with InuYasha and his mother after Inu no Taisho went to go investigate the rumors of the dragons invading the lands, and enjoyed picking on the hanyou rather mercilessly, especially in the few times that Sesshoumaru came to visit.
By the time InuYasha's mother died, leaving the hanyou child (now eleven) an orphan, Sakura had already gone off to live with Youko, and train to be strong under his tutelage. InuYasha grew up alone, and as an outcast to both youkai and human society, until the time he met Kikyou. Unbeknownst to InuYasha, the essence of Order/Law continued on in his body, in the form of Tessaiga, a sword forged from the fang of the great Inu no Taisho.
Sesshoumaru had lived with his own mother until he was the human equivalent of fourteen, when he'd set out to try and surpass his father's great strength.
And with this knowledge in hand, we can begin our adventure!