Masashi Kishimoto owns Naruto, but this story is all mine. My first story so please comment on anything that might seem strange, if you want the story to continue or have any interesting ideas where it could go.
It was a calm morning in Konohagakure no Sato. People were just waking up and everything seemed perfect, well as perfect as a morning in shinobi village could be. Of course peace couldn't be everywhere. In Konoha's orphanage a young child, no older than four, opened its eyes and yawned 'Another day in this godforsaken place.' Sitting up, the child grimaced 'If this goes on I might go crazy from boredom.' This was no ordinary child, because this child was hated by the whole village. In another world, this child is an idiotic loudmouth named Uzumaki Naruto. In this world the child's name is Uzumaki Naruto too, the difference between these two is simple, our child doesn't know its name and caries memories of long since thought dead Kawa Jashin.
To enlighten you on his history, well… Kawa Jashin lived in times of Senju Hashirama and Uchiha Madara. He was a leader of a feared clan residing mostly near Land of Water that was mostly nomadic. Upon Konoha's founding, the first Mizukage asked them to join the Kirigakure no Sato. Jashin, seeing this as a safe place for his clan, immediately accepted. After all, they were feared and a rather tiny clan, counting about twenty people. The problem? The clan was at the time near the Land of Whirlpools, homeland of Uzushio, the allies of Konoha. In order to weaken the Kiri, the Uzumaki clan attacked the traveling Kawas. The fight was very brutal but overall quite short, only a few hours long. In the end the Kawas were defeated and killed, this didn't come for free to Uzumakis as they lost tens of fighters and seal masters. The deed was done. Kawa clan was lost to time. That is… till now.
You are probably wondering how did this happened. Well it was actually a series of unfortunate events. Firstly the Uzumakis didn't or more like couldn't kill Jashin so they decided to seal his chakra and soul into one of their own. This wouldn't be so bad if the seal wasn't unintentionally passed down through generations until it was given to Uzumaki Kushina and through her to Uzumaki Naruto. Second event leading to this… tragedy? was the decision of Konoha's fourth hokage, Namikaze Minato, to seal Kyuubi no Yoko into his new-born son Naruto. Third action came from Konoha's counsel to seal the mind of a few hours old jinchuriki. The seal they used was supposed to limit his intellect, but it actually caused him to become braindead. The fourth and final event was the attempt of Kyuubi to save the mind of Uzumaki Naruto. After all, what good is a braindead host? Simply put, he used as much chakra as he could to destroy the seal. Instead of destroying the seal on Naruto's mind, he destroyed the seal containing Kawa Jashin that then took over Naruto's body… and that was the end of Uzumaki Naruto.
'When I said "If something didn't happen I'd go crazy" I didn't mean to get kicked out of the orphanage.' These were Jashin's thoughts as he was walking down the street just some hours after he woke up. 'Oh well, what's done is done. The real question is: Are the villagers glaring at me because of my vessel or because they hate this vessel's family?' Staring around himself and pretending not to notice the glares, he realized everyone was whispering about something. Carefully getting sufficiently close to hear parts of whispered conversation, he heard: "Did y…ear, it's...at demon." "Shhh, we aren't su…sed to tal…bout it."
That was enough information for Jashin, he started sprinting away, somewhere without other humans. 'How could they find out about me?! It shouldn't be possible for them to even remember the name Kawa Jashin! So how? How did they found out?! They hardly paid me any attention, so how did they notice I'm not a little brat?' Breathing hard, he finally stopped at some empty training ground. Falling under a tree he tried to calm his breathing and reassure himself that this discovery isn't true, that he made a mistake. 'Alright, alright just take slow breaths. In. Out. In. Out. Good. Now, thing everything over again. No hasty declarations. What use could Konoha have in keeping an enemy alive and relatively unharmed? The answer was easy: "My kekkei genkai!" Truly terrified now, he scrambled up and started pacing back and forth. 'But CAN I even use it anymore? I mean I'm in completely different body so my bloodline should be gone too. Right?' Still pacing he run a hand through his short hair. "First thing first, I must find out what abilities I have left."
So turns out that nearly all of his abilities were gone, worthless or worse… couldn't be used in his new body at all. Like his kekkei genkai and with it his taijutsu. Ninjutsu was impossible for him to learn in his last life. Genjutsu was never his forte and don't let him started on the godforsaken fuijutsu. To sum it up, his chakra wasn't awoken, his reflexes were shit, his instincts were all messed up and anything that seemed to work was his sensor ability. 'Life really is a bitch.'