Naruto AU where Naruto isn't as optimistic as he is in canon and as a child, he's a lot quieter, isolated, more depressed.
In the orphanage, he never had any reason to talk because no one was around to hear him anyway, so when he was thrust into the academy with a bunch of screaming kids, he didn't really know what to do with himself. Everyone somehow already knew each other, whether they were clan kids who saw each other when they were with their parents or they just met each other in the playgrounds Naruto's never been to.
Naruto was an other to the kids in his class, with his strange whisker marks and his knee-length blindingly gold hair, so they moved around him, talked over him, looked past him. Plenty of the kids were OK with acting like his existence was passing while they were in class, or, they were... right up until the day ended and it came time for their parents to come and walk them back home.
When the teachers announced that they were finished for the day and that their parents were waiting outside for them, many children rushed out of the room to tell about their amazing first days at the ninja academy. Naruto rushed too, not because he had somebody waiting for him, but because he couldn't stand sitting in that room any longer, with that teacher who glares at him and the kids who don't talk to him.
Outside looks nicer. The sun is shining and casting a golden hue on the scene of kids and their families outside of the schoolhouse. This scene, however, immediately turns dark when Naruto walks out. The first person to see him is a plump lady with brown hair talking to her daughter. She's facing the door, and when she sees Naruto with all his bright blue eyes and long blonde hair and whiskers she gasps, quite loudly, then begins tugging her daughter away from the academy, away from where Naruto is standing.
The noise attracts the eyes of a few other parents. who have the same reaction, though slightly louder than the woman. These people talk. They yell things like "It's the demon child," and then they rush home. The children are confused since none of them have even met Naruto before, how could all of their parents know him? Naruto, in the face of multiple way too big, way too scary, runs away, all the way back to the orphanage where he is greeted with a locked door and his meager belongings on the steps in front of the door.
The next day at the academy, the kids look at him. They sneer, and they taunt, and they repeat all the things their parents had told them about him the night before.
Naruto was excited to graduate from the academy. He remembers when Iruka-sensei was teaching the class about genin formations, and about how in Konoha, your team is like your family. Naruto dreamed about family.
Your genin team is not your family. Naruto learned this about a month into training with his new team. Uchiha Sasuke was a haughty, self-centered kid who never gave Naruto the time of day. Haruno Sakura... why was she even a shinobi? All her desires and motivations were centered around the Uchiha boy, even though he treated her no better than he treated Naruto. Kakashi-sensei was... there. He taught Sasuke lots of cool jutsu... he hardly even looked at Naruto. When he did, he looked blank. Not that you could tell much with his mask, but after a lifetime of looking at people and seeing the looks in their eyes, Naruto knew that the man wanted nothing to do with him. Nothing more than necessary, at least; he still instructed Naruto when he needed to, but that's kind of his job.
By the time of the chuunin exams, Naruto had gotten quieter. He had made no moves forward with his team, and no matter what he just couldn't find a way to. Why did Kakashi-sensei even think that they were ready for the chuunin exams, anyway? The team was going to fail because of him.
After the botched chuunin exams, Naruto expected... something; literally anything. That lazy Nara had gotten his chuunin vest even after he forfeited. Naruto suppressed the Ichibi with a brand new summons and a transformation jutsu. Why doesn't that get any
recognition? Does no one seriously want him here? Why the hell was he even born? Why the hell did his parents take one look at him and decide he wasn't worth raising? Why was he dumped in place where people only wanted to hurt him? If he has no place in Konoha, why doesn't he just leave?
In the dead of night, two days after the Suna delegation left Konoha, Naruto took his sack that was hanging on his closet door, packed a few clothes, some food, the money he made to make sure he would never starve again, and closed his apartment door for the last time.
Two days later, a worried Kakashi who was concerned over the sudden disappearance of one of his students invaded his home and found... nothing. No clothes, no food, no money, no scent. Naruto was gone.