Sometime near the middle of September, Konoha got sick.
Everyone from Villagers to Shinobi each grew a severe rattling cough and bone-chilling colds. Their faces flushed and their bodies grew weak. The disease traveled on from human to human, seemingly having no taste for any of the animal life.
Konoha was quarantined. No one was permitted to enter or leave the village as the contagious illness only worsened. The source of funds dried up, eventually even food had to be rationed out until only one meal a day was permitted.
Shinobi rations kept them all alive.
No one could tell exactly from where this disease had mysteriously originated. Or even exactly when it had started. For it was the lesser individuals living in the low down corners of the earth who had taken ill first, and where nobody would lay concern.
But when the plague spread to the prominent Clans of Konoha, then it was noticed. The spread didn't take too long, but it's effect was permanent and disastrous. They named the sickness Nine Tails, after the nine great Clans to fall victim to it.
The population of Konoha was reduced to a third of it's members.
But one man managed to save them all. By voluntaring to submit his body for experimentation on the disease, he had managed to help them find a cure. Even though it cost him his life.
The Fourth died for his village. On this day, Naruto was born.
Sasuke's entire family had fallen ill to the diease. He had just gotten the bone-wrecking cough when the cure was distributed. But even with that, his parents never really recovered right.
They got cold in the evenings and sometimes couldn't wake up in the morning. Sasuke could remember desperately shaking his mother's arm only to receive a half-awake turn of the lips.
It was so lonely. He could hear his voice echoing against the walls, bringing with it a stagnant air that lingered in the chilling quiet.
One day, Sasuke came home to find what was left of his clan lying dead in the street, covered in their own blood.
Mizuki laughed at Naruto, mocking him.
The little boy was crouched in the corners the old wooden shack made, curled around a scroll almost as big as he was. The shadows almost hid him. If only his pursurer wasn't right in front of him, radiating a killer's lust..
But he wouldn't believe it!
Naruto's teacher couldn't be true. That had to be a lie beneath those sneering lips staring at him. There was no way he was only ordinary.
Naruto was special. He was important.
He would be somebody.
Kakashi smiled down at the child, and rubbed the boy's blonde head.
"Who were you talking to just now?" He'd asked, his eye a voice of amusement.
Naruto looked up, all brilliant smiles.
Note: I blame this entirely on a line from NoNoWriter's story, Running Thin. Which said; "Do I have to be high or unconscious before you can talk to me!" The author's ID is: 1128683.
Simply put, the Kyuubi (as it means Nine Tails) was the disease that struck Konoha. Mizuki only targeted Naruto because he was convenient. He failed the Graduation exam, and was so eager to pass that he'd do anything. Even steal the forbidden Scroll of Seals.
What Mizuki probably told him was something along the lines of "You're worthless. You'll never amount to anything. What a total waste of a life." Naruto didn't like that. But without the demon chakra, he might not have beaten Mizuki. If he didn't, an Anbu probably found him, or Iruka. Who knows.
He might have tried the test again the next year and passed then, or never became a shinobi at all.
Maybe Kakashi is just passing Naruto in the street and hears him talking to himself, and, being a curious one, asked the little boy who he was speaking to.
It could be a split personality, or a desire to be noticed. That he was so lonely he had to create someone just to talk to. Naruto's mind is a curious thing..