It could be Orochimaru. He's always been interested in experimenting and causing chaos. Maybe he wants to use Naruto's parents' forgetfulness as a way to study the Uzumaki clan's mental state or something related to their chakra. He might see Naruto's vulnerability in this situation as an opportunity to get closer to his goals.
Well, it could be that Naruto's parents, Minato and Kushina, somehow lose their memories of him. Maybe due to a powerful jutsu gone wrong. Naruto then has to deal with the pain of seeing his parents act as if he doesn't exist. He might try to find a way to reverse the effect, all while still facing the usual challenges in the ninja world.
In this kind of situation, Naruto might first feel extremely sad and lonely. He could start by trying to prove himself to others. Maybe he'd focus on his ninja training more than ever, using it as a way to distract himself from the pain of being forgotten by his parents.
One possible reason could be a curse. Maybe some enemy put a curse on Naruto's parents that made them forget about him. It could be a way to get back at them by targeting their most precious thing, which is their son.
Common themes in this type of fanfiction are abandonment and its consequences. Naruto's world is turned upside down by his parents' forgetfulness. Another theme is the search for acceptance. He wants to be accepted by the village and by others, but it's harder when he has this gaping hole in his family history. Also, the theme of inner strength is present. He has to dig deep within himself to find the strength to carry on. It's about how he can build his own self - worth when those who should have given it to him from the start (his parents) are absent.
Perhaps in this fanfiction, Naruto starts to have dreams about his parents where they seem distant and unrecognizable. This makes him search for answers, leading him on a journey where he uncovers secrets about his family that were long buried. As he digs deeper, he realizes that there were forces at work that made it seem like his parents forgot him, when in reality, it was a much more complex situation.
If the fanfic had a very niche concept or a plot that was a bit too different from the mainstream Naruto stories, it could have been forgotten. For example, if it focused on a minor character in a really unique way that not many people were interested in at the time. Also, if the website where it was hosted had some issues, like shutting down or losing data, that could contribute to it being forgotten.
In such a fanfiction, Naruto's character development could be really interesting. Without the support of his parents, he might become more self - reliant at a very young age. He'd have to learn to fend for himself, which could make him tougher both physically and mentally. Maybe he'd be more distrustful of others initially because he's been abandoned. But as the story progresses, he could learn to open up again through new friendships, like he did with Sasuke and Sakura in the original series, just in a more complex and painful way.
Well, there could be characters like Iruka - sensei. Since Naruto has been forgotten by his parents, Iruka might play an even more important role in Naruto's life, becoming like a surrogate father figure. Another character could be Sasuke. Sasuke, who also has his own family issues, might either be a source of understanding for Naruto or a contrast to his situation.
Well, Naruto is a really strong - willed character. So, at first he'd be really hurt. But then, he would probably try to figure out why his family has forgotten him. He might go on a journey to find answers, all the while dealing with the pain of this rejection. He could also be angry at his family for forgetting him so easily, especially considering all he's been through.