So... you all remember when Sasuke was bitten by Orochimaru and got the Cursed Seal? It used to pop up in so many stories but honestly people forget one major thing... one massive thing even. In the story, Sasuke was forced to relive the traumatic event of his family's brutal murder while being taunted by Orochimaru. I think the jutsu, by nature, needs to be mentally accepted and it does anything to do that. To make the victim crave power by some means for some purpose.

For Sasuke it used his drive for vengeance. For Kimimaro it was to serve Orochimaru... you get the idea.

What would happen if, during the Sanin fight, he marks Naruto as a final middle finger to his old Friends. He knows it won't kill him, Naruto has Tsunade and the Kyuubi to help... but what he does not expect or even know is that it has other effects. Naruto sees his old life, over and over again, the loneliness, the neglect of the village and the Third. Jiriaya throwing him down the canyon, Sakura being Sakura, Kakashi being a craptastic teacher. It chips away at his decency and light until it finally reaches his truer self, one he repressed. The darkness that he never even in canon dealt with...

When he awakens he is not the same and he starts to shift the longer he is alive. He can no longer hide behind the mask of happiness, his old niaviety forced away. He craves knowledge and power, calmer than before. When Sasuke defects he only goes after him to follow suit, to find Orochimaru and thank him.

The Curse doesn't even have to stay on him, Naruto just needs to be exposed to it and boom you have realistic bolstered personality changes. You have someone that has a realistic need for power, a realistic need for change, a desire for his own strength to never be so helpless and reliant on others...

Or maybe he does not go with Sasuke and just Runs away entirely... Or maybe he stays in village and grows in a darker way, becoming ANBU...

Feel free to use this, anyone, I might... if I did, which latter path should I go down...

Love you all!