It could be a member of Naruto's family who is fueling the neglect. Maybe an older relative who believes that the sister has more potential or is more worthy of attention and resources. This person could actively try to keep Naruto down.
Another aspect could be the relationship between Naruto and his sister. If she is the favored one, she might initially be oblivious to Naruto's pain. But as the story progresses, she could realize how wrong it is and try to make it up to him. This could lead to a complex family dynamic exploration in the fanfiction.
In such fanfictions, Naruto's character often becomes more self - reliant. Since his family neglects him for his sister, he has to find his own way. He might become more withdrawn at first, but as time passes, he could turn this neglect into a driving force for self - improvement. He may focus on training harder, making friends outside the family, and developing a stronger sense of self - worth independent of his family's recognition.
A plotline might involve Naruto starting to act out in negative ways to get his parents' attention. He could start getting into trouble at school or in the village. Maybe he would start to explore his own powers in secret, away from his family, and discover some unique abilities that he then uses to show his parents what they've been missing. Also, there could be a plotline where Naruto tries to build a relationship with his sister in secret, hoping that through her, he can get closer to his parents.
This kind of fanfiction is really exploring the darker side of family relationships. Naruto, who is already a character with a difficult past in the original story, would be even more burdened here. The neglect from his parents could make him develop some negative traits. He might become resentful, not just towards his parents but also towards his sister, at least initially. However, this could also be a setup for a great character arc where he overcomes this pain and learns to love and accept his family again.
Well, it could make him more desperate to catch up. He might become more self - doubting at first. But then, as he realizes his mistake, he could develop a stronger sense of determination to overcome his lack of training. For example, he might start training in more unorthodox ways to make up for lost time.
He might focus on his training more. By pouring all his energy into getting stronger, he can distract himself from the pain of family neglect. For example, he could spend long hours practicing new jutsu or improving his physical abilities.
Naruto might try to seek attention elsewhere. He could focus on his training more intently. By pouring his energy into becoming stronger, he distracts himself from the pain of parental neglect. Also, his friends could play a crucial role. Their friendship might give him the sense of family and belonging that he lacks at home.
One possible story could be that Naruto discovers his unique bloodline abilities later in life and realizes that his parents' neglect was partly due to fearing his power. He then has to come to terms with this and learn to control his abilities on his own.
In the 'naruto neglected by his mother fanfiction', Naruto may have a different approach to his ninja training. Instead of being motivated by the desire to be recognized like in the original story, it could be a way for him to escape from the pain of his mother's neglect. He might train harder and more recklessly, putting himself in danger because he doesn't really care about his own well - being as much, since he feels so unloved at home.