From reading chapter one, this piece so far holds promise. There are a good deal of imaginative things occurring. But there are also a few things I would like to bring to your attention.
Please spell out ordinals. While styles vary about when and where the cutoff is for spelling out numerals, ordinals are always spelled out in prose.
Please don't put -------- Flash Back -----------. It's distracting, as it causes me to completely abandon the suspension of disbelief heretofore established. If you'd like some thoughts on this, there's a discussion thread in the forum here:
http://www2.adultfanfiction.net/forum/index.php/topic/25862-flashbacks-in-fiction/
Before adding hyphens into words, please verify that they need them. Spell check probably won't catch misspellings like "six-teen" because the word has a hyphen in it, and it doesn't recognize that it's incorrect. If there's any question, you can always Google the word. In this case, Google shows results for the correctly spelled word "sixteen".
Please be careful of using blond(e) and brunet(te) as descriptors. Blonde is the feminine descriptor, blond the masculine. You have blonde in reference to Naruto, where you've clearly established him as masculine.
To be completely blunt, the first few paragraphs (all of them preceding your "@" line break) seem forced. It reads as though you're attempting to introduce a section that you had already written.
Honestly, with the flashback being this early in the tale, I think it would serve your story better to have the section as a prologue, so that the reader is fully aware that the events are taking place at a different time when they get to chapter one.
The impact of the scene where Sasuke draws the blade and pierces Naruto and Sakura is diminished by the lack of visible interaction between the characters preceding this point. While it may be easier to summarize the events by telling the reader what happened, it helps the reader to become more involved if you "show" the events. For example, instead of telling me that Naruto tried desperately to talk him out of it, show me the conversation. This builds character interaction, as well as tension, laying the groundwork for further development in later chapters. It helps the reader to become more engrossed in your tale, ultimately developing more affinity for your characters.
If you did make the 'flashback' section into a prologue, it would help you to expand on these details without deterring the reader with an overly long chapter. I realize length is always a consideration when writing chapters (how much is too much, after all), so separating this out would help to draw the reader more deeply into your tale.
I see the same issue with description versus narrative with the caravan battle. It would be much more enthralling to read a description of Naruto disabling the bandits than the simple statements that the event occurs. Rather than simple declarations, demonstrations of his ferocious fighting would draw the reader into the story more effectively. My only concern in expanding on this is making Naruto seem invincible, thus turning him into a "Stu," which is certainly something that you don't want.
In regards to the bandit who was tossed off the cliff: you have him being injured via a puncture directly through his lungs. Yet when you describe his flight from the precipice, you state he screamed as he descended. While it is possible to scream with a punctured lung, it is also highly unlikely, given that the lung being punctured causes shortness of breath. Drawing enough breath to scream through the entirety of a fall from a great height would be nigh impossible for someone with such an injury.
I don't want you to think that I didn't find your story interesting; the premise isn't something that I've read before in this section. I do hope you'll take my comments under consideration, and continue to improve in your craft.
Happy writing!