Disclaimer: I do not own Naruto.
Chapter I - In which a prologue is made and various facts are explained
I cannot conceal from myself the anxiety which grips my heart at this moment. I close my eyes in painful concentration and bring my hands together in ram seal to channel my chakra. My shadow-self appears in the middle of the seal matrix I've been drawing on the onyx stones of the basement floor of the tower. I prepare myself.
In my studies of summoning and time, of sealing, I've discovered that affecting the time is easy. As a matter of fact, every chunin learns how to do it in the form of body flicker which is essentially slowing time a little bit while fastening how we perceive it a lot more. Traveling in time is somewhat harder, but not much. Every summoning uses pocket dimensions that are created and destroyed almost instantly to go out of our reality and enter it again at a desired point and time. Time aspect of it is rarely used because, while it is easy to archive it, it is immeasurably harder to remain there. One might almost say impossible. While that goes to prove that matter and energy of the universe is finite and unchangeable, the thing we must pay attention is the word almost. There is a small window of opportunity to act. A second at most, but sufficient for me. But, again, all of this is just theory.
I look at my shadow. Take a few steps forward and put my left hand on the the trigger of the matrix. I pour all the chakra I can in.
Everything that is becomes that isn't...
Namikaze Naruto
...or not. I could not really know. Last thing I remember is how he (I) looked at me like kicked puppy searching for forgiveness for something he didn't do.
Then I woke up here.
A child's body. Check. Shadow possession must have worked then. Since I didn't invented it yet, let me explain what it is. It basically works like Yamanaka's body possession but instead of doing it yourself, your shadow clone does it. Clone loses its matter in the process and becomes pure chakra energy existing within target body. While it sound awesome, it really isn't. The clone can't control the body he is in. Not while the target is still in. Foreign shadow clone chakra can't exist within the target body since the body's chakra of life is already there. What it can do is to take control of a newly died, not much damaged corpse, or the body of an another possessor like a Yamanaka until the real owner returns.
But what if I (he) send a clone to possess myself, what would happen then. Having the same chakra of life, will the two chakras merge? I guess you already know the answer. Just let me correct a little mistake you might have made: Instead of merging, the older, more powerful chakra will take over. When you create a shadow clone you send a tiny part of you chakra of life. That is what enables you to take the memories clone has. But my younger self had not sent anything out, so there were nowhere to return to and thus I have replaced him completely. Somehow I am a living Naruto now. I know that because I can feel my chakra replenish.
So, a child's body. Check.
It is everything else that is wrong.
For starters, I were going to save the world from the Kyuubi vessel and somehow I am the vessel now!
What the fuck is going on here?