Disclaimer: I don't own nothing but the lint in my dryer. maybe.
It was first noticed when after an ambush attacked team seven on a routine border patrol and Kakashi noticed that one of the Bandits was missing a large chunk off of his upper arm and Naruto had some blood on his face. When questioned about it, Naruto simply said, " I may have bitten him." After looking around some more and still not finding the missing piece of flesh, they resumed clean up and burned the bodies and continued their patrol.
Some time later after they had returned to the village, Kakashi was giving his oral report to the hokage, Tsunade when he mentioned the missing flesh. Tsunade, not seeing the big deal, told Kakashi not to worry about it even if naruto DID bite someone while attacking. She recommended that if he wanted to, he could bring Naruto to Jiraya to have his seal checked if Naruto continued to bite while attacking.
After several incidents of bite marks appearing on various dead enemy nin and bandits and some animals in nearby forests, Kakashi contacted Jiraya about his worries. After telling Kakashi that Naruto was absorbing the Kyuubi at a faster rate than when he was a child and that some of the more animalistic traits might pop up every now and then, and that biting was something Naruto had been doing from an extremly young age there was nothing to worry about. Jiraya then told Kakashi, half-joking, that if he starts eating his bite victims then that was the time to worry.
After several months of just bites, Kakashi starts to regard the habitual response as normal for naruto and forgets about any worries he might have had. He doesn't notice that Naruto had been watching him watch him when he fought, particularly when he bit people. Becoming more secretive with his biting problems, he starts to swallow the blood and flesh he bites off of his enemies. Coming to enjoy the taste of human flesh more and more, He starts to keep some of the human bodies from his solo missions in a sealing scroll for later consumption.
After nearly a year of eating humans Naruto notices that the Kyuubi's mind was starting to merge with his, leaving his personality dominant with a complete set of Instincts for survival in the wilderness. The first time he encounters the Akatsuki, he was alone and It didn't take long for Kisame to notice his instincts screaming at him to run away from Naruto as fast as possible, well, more than usual any way. Paying no attention to his instincts as he usually did, he tried to attack Naruto, only to be completely blindsided by a kick to the chin and a BITE of all things ripping a chunk of flesh from his leg. Landing somewhat awkwardly due to missing a chunk of leg, He pales as he watches naruto chew and swallow the missing part of his leg. Itachi then decides that the new (to them) development needed to be reported before they tried to bring in the kyuubi container, that and Kisame really should get his leg tended to before he bled out, called for a retreat and left.
After Kisame and Itachi left Naruto continued on his way back to the village returning from a courier mission to Suna. Upon reaching the Hokage tower, he reported his mission and encounter to Tsunade and after staying to discuss speculations about weather or not the Akatsuki knew that the Kyuubi was almost completely gone or not, he headed home. After a relaxing meal of Ramen with chunks of some unnamed bandit added for flavor, he went to bed to dream of eating kisame after slicing him up to make sushi.
In the morning Naruto received a visit from Jiriya to check on his seal's progression, and to catch up with each other, he left to get another mission.
After another six months Naruto ran into Sasuke and his team. After a little not so friendly pre-battle banter, they attacked each other and Sasuke was surprised when Naruto smiled and instead of his normal slightly pointed teeth, Naruto now had teeth a shark would be jealous of. Clearly off balance, he demanded, "Just what the hell did you do to yourself Naruto?" Grinning widely and showing nearly all of his new(ish) teeth naruto said, "I have almost completely absorbed The Kyuubi no Kitsune, is what I have done." After that they returned to fighting each other until Sasuke could hear an ANBU patrol heading their way. Running off to avoid being caught and returned to Konoha, he shouted as he ran off, "See ya around naruto,and next time maybe you wont have better teeth eh?"
After a few years pass and Sasuke kills Orochimaru and returns to Konoha, Naruto eats many more bandits and nin, A few encounter with the Akatsuki, with kisame having a slight limp that made Naruto smile whenever he saw it, Pein comes for Naruto. Pein and Naruto meet for the first time in a small village that no one really cares about and proceed to duke it out. After almost being trapped Naruto shouts at Pein that even if he did capture him, they would never get the Kyuubi seeing as he had completely absorbed him at the time. Shocked and in denial, pein calls upon his last reserves and knocks Naruto out. Taking him back to the Akatsuki's latest hideout, he calls all the members still alive to begin the extraction jutsu. All seems to be going well and the jutsu starts up, but after a while, they begin to notice that nothing was coming out. Trying harder, they get the same result. Since they waited until Naruto was on a short vacation to capture him they didn't have to worry about anyone interrupting them so they tried one more time. Getting nothing yet again and thoroughly exhausted, they chain Naruto up, give him some sort of injection to keep him knocked out they left him in the extraction chamber planning on trying again in the morning when they were rested, and leave to go to bed. In the morning, the Akatsuki reassembled to try again, but stopped noticing that Kisame wasn't with them. Looking around for him and not finding any trace of him they decided he went out for awhile and would be back after a few days or something, they decided to rest and do whatever missing nin did because without him the extraction couldn't proceed any way. The next day Deidara and Konan were missing and still thinking nothing of it the rest continued to wait, completely forgetting about Naruto. Over the next week Zetsu, Tobi, and Itachi disappeared leaving Pein alone. It was then that he remembered Naruto who had been left in the extraction chamber and might be dead by now. When he went to check, he wasn't there. Later he found a note from Itachi stating that as Kisame deidara and Hidan were gone, he was leaving and to not to try to find him as was going to find a tropical island to live on. After a few more days of being alone he found out what happened to the other members of the once mighty Akatsuki, He was killed and eaten just like every one else, exepting Itachi, who knew when to get the hell out of dodge.
Having a few more days left of his vacation Naruto left and started to head back to the village. Along the way he ate approximately twelve earth inn before returning to the land of fire. Before He was within sight of the village walls he ran into Sakura who then proceeded to berate him for not being there for missions, even though she had been told several times that he was going on vacation. In a slightly foul mood from her screechy voice and amateur insults Naruto decided to eat her. Drawing a single kunai and catching sakura by surprise, he slit her throat and butchered her for later consumption, sealed her up and headed home. When he got home he decided to make some stirfry and rice for dinner using sakura as the main ingredient. When he was putting everything on the table Iruka came by to see if he wanted to got to dinner with him and seeing iruka for the first time in several weeks, Naruto invited him in to share his dinner.
Every few weeks a shinobi would disappear and no one would know what happened. Naruto ate well for years.
Well what do you think? I am new at writing so any input is nice.