This is AU, clear and plain, just a little what if it wasn't the Kyuubi that got sealed into Naruto as an infant.

Prologue:

"You're certain this demon is after the woman and her unborn child," the Fourth sought to clarify, this whole situation was unsettling and coming together far to fast for his liking.

"With absolute certainty- He will stop at nothing to get to this woman."

"Do you know why?"

Takemaru scoffed, "He's a Demon, who cares."

Turning away from the Fourth, Takemaru spoke briefly to some of his warriors of Setsuna, then turned from them as well and headed into the palace where the woman was giving birth to her child.

"This bodes ill…"

Then IT came, pausing only to bay at the lunar eclipse, then transform itself to appear as a man, tearing through all his well planned defenses like a torrent of blade and miasma. All manner of man, Shinobi or warrior of Setsuna, were gashed, slain, or simply blown back. The Fourth himself was slashed and blown away by the demon's rampage before it entered the building.

"Set it a fire! Demon and Victim alike- he MUSN'T escape!" the Takemaru called. The Archers at his command unleashed a rain of fire, in moments the palace was ablaze.

A the Fourth Hokage pulled himself to his feet he saw only the last moments of Takemaru's fight with the demon. The woman fled out the back carrying her white haired infant as Takemaru was slain. The demon took an unsteady step past Takemaru's body, but as he did the ceiling fell in cinders, the whole building at last came down around the demon. The Forth stood himself steady, noticing a free flowing wound on both his temple and his shoulder.

Rising from the flames the demon stood, one of his arms dangling limply at his side and all but torn free by the rubble. With a pained look on his face the demon took to his true form, rising taller than the palace he had been fighting in moments before, he lifted his head and gave a sorrowful bale at the now-returned moon.

"Such power," the Fourth acknowledged in mix of awe and horror. "I may have to resort… to That seal…"

The demon looked down at the Fourth as he got in the demon's way. The demon steadied himself for one last fight…

Sometime later an awareness returned to the demon. He seemed unable to move-

Eyes opened, he could see through them, but they weren't his. Lips opened as a child's cry echoed with his own wail of disbelief.

And suddenly a pang of heartache crossed his mind, tied in with an overwhelming sense of relief.

"Inuyasha…"