From the desk of Hiruzen Sarutobi,
To understand, we have to go back to the very beginning. The beginning of our time, the time of the shinobi… There was once a great man called the Sage of the Six Paths. He was revered as a god as he possessed the Rinnegan. He is most known as the father of all ninja. However, there is more to this story that has yet to been told. Little did most know, the Sage had a lover named Kuromei Mitsukai, meaning dark angel, whom was an immortal goddess. She was very beautiful and strong and also had many psychic powers and was very powerful. She fell in love with the Sage and bore him many noble children, resulting in the Uchiha clan. Soon after, though, the Sage fell in love with another, Karoyaka, Kuromei's sister, and goddess of light. Karoyaka also bore the Sage children, starting the Senju line. Kuromei, angry and betrayed, sought out her brother Yokoshima, a divine but evil being. Swearing revenge, she joined with him and they had children. These children, being direct descendants of two immortal beings, were very powerful and soon feared by all. They become known as junketsu, or purebloods.
With the past histories of their mothers and therefore clans, the Senju and Uchiha were quick to become rivals and sworn nemeses. They fought endlessly, having many wars and bloody battles. The Uchiha clan then sought out the assistance of their half brothers and sisters, the purebloods. They allied together for many years until a grave betrayal occurred. Madara Uchiha, then the leader of the clan, seeked to take the purebloods power for himself. Upon discovering this, the junketsu broke off their alliance with the Uchihas, and tiring of fighting, went into hiding.
They were soon forgotten until one day when a Leaf jounin, Fugaku Uchiha to be exact, while on a mission, came upon a young female pureblood. He attacked her, taking her for the enemy. However, she subdued him before claiming she did not wish to fight. He was soon confronted with the woman's husband also and the two purebloods explained that they didn't want to hide anymore and wanted to use their powers to establish peace in the shinobi world.
Not long after that fated meeting, Fugaku invited the two to his home. He had just recently become the leader of the Uchiha clan and also hoped for an establishment of peace. The two purebloods became fast friends for Fugaku and his wife, Mikoto. Soon, an agreement was made for the clans to be joined in alliance once again. A union between two children of each respective clan. An Uchiha son and a pureblood daughter.
Years passed and soon the pureblood pair gave birth to a daughter. The treaty they had with the Uchiha clan did not go into effect until the children reached the proper age of eighteen. So, the daughter was put into hiding for her safety, for her fear of her life if others heard of this arranged marriage. However, it did not go as planned. When the girl was five, one of her uncles, also a pureblood, sought her out, desiring her hidden power. Within the junketsu was a prophecy that a child would be born as a reincarnation of the legendary mother, Kuromei. She would be the most powerful of all purebloods yet and become ruling Queen. Even so, her mother and father did not wish a life full of blood, death, and darkness for their beloved daughter. Therefore, they fought to protect her and the father died fighting his brother, the girl's uncle, while his wife used her last remaining magic to seal away the child's power and erase her memory.
The girl was found by Itachi Uchiha and brought back to the village, having no recollection of who she was or what had happened to her dear family. The Uchihas took her in and raised her as their own. A year later and all seemed quiet until the seemingly peaceful time was disturbed. Madara Uchiha, back from the grave, heard news of the prophecy and also of the young girl induced into his clan. He investigated and found this was his chance to once again take the purebloods power for his own. However, Fugaku refused to hand her over. Madara , in anger, released the Nine Tails, making it seem like the Uchiha were attempting to betray the village. To fuel the flame, he confronted Danzo and convinced him to assist him in destroying the Uchiha clan. Danzo then proceeded to sway the elders. An order was made to take away the girl from the Uchihas and also break off the marriage arrangement between her and a son of the clan. Fugaku, furious, was driven to defy the elders and set out against the village. In response, I had no choice but to make the final order of assassinating the rebellious clan. All of my attempts at peaceful negotiations have failed and so, Itachi Uchiha has been sent on a mission to kill his entire family. I am deeply ashamed of what the situation has come to and I will never be able to put into words how sincerely sorry I am for why things had to be this way. Itachi begged me to spare his brother, Sasuke's, life but also the life of the young girl he had rescued. I concurred, fulfilling his last wishes to me. I thought it was the least I could do. I took the girl and put her into a foster family and so not to arise suspicions, made sure it was a non-ninja family.
By now, you are probably wondering who this mysterious girl is. Well, let me tell you who she is. The daughter of two powerful purebloods. A direct descendant of gods. A possible reincarnation of the immortal, Kuromei. And most of all, the fated wife of Sasuke Uchiha, the heir to the Uchiha clan. Well, this girl is none other than Sakura Haruno.