Full sumary, if you don't want to read it, then you can skip to the first chapter
When the kyuubi no kitsune attacked, Hundreds of lives were lost, both civilian and ninja alike, his tails caused all kinds of natural disasters with a swing.
The ninja fought bravely, trying to contain it, but they couldn't do much, in the end it fell to the fourth hokage and his dying wife to stop it.
They sealed the fox inside of their newly born baby, with hopes that it would never again rampage, and they sealed their consciousness as a failsafe, to help their son when he needed it the most.
But the sealing of his wife went wrong, and her consciousness would be left to roam her son's mind, until such time he found her, and trapped inside him until the boy found a way to release her