He might try to prove himself. Naruto has always been a determined character. He could focus on his ninja training more intently, aiming to show everyone his worth despite being neglected. Maybe he'd also start to distance himself a bit from his family situation and form closer bonds with his friends like Sasuke and Sakura, who might understand and support him through this tough time.
It's popular because it explores a different side of Naruto's story. The idea of him having a sister who cares when others don't adds an interesting dynamic. People like the concept of family loyalty and the sister being a support system that Naruto was lacking in the original story.
In such a fanfiction, perhaps the village's needs are always put first by Naruto, and his sister gets the short end of the stick. For example, he might not be there to protect her when she faces some bullies in the village just because he's too busy with village affairs. This could cause her to doubt Naruto's love for her, and she might even consider leaving the village in search of a place where she feels more valued.
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.
At first, the relationship might be strained. Naruto could be jealous of his sister's favored status. However, as the story progresses, his sister might start to see the injustice Naruto faces and try to bridge the gap. They could gradually develop a more understanding and loving relationship.
Well, in some fanfictions of this kind, Naruto's sister is often portrayed as having a special bond with him. She might have a unique ability that she uses to shield Naruto from the emotional pain of being neglected. For example, she could have a power to absorb negative emotions, and whenever Naruto is feeling down because of the neglect, she uses this power to make him feel better. There are also stories where she tries to expose the unfair treatment Naruto is getting to the village elders, but has to be very careful as she doesn't want to put Naruto in more danger.
It could be a jealous ninja in the village. This person might see Naruto's sister as an easy target since Naruto is often preoccupied. They could spread rumors about her or try to make her life difficult at the ninja academy, taking advantage of Naruto's absence.
It could be that his sister has some special abilities or talents that the family or the village values more. For example, if she has a very rare and powerful bloodline limit, everyone's attention would be drawn to her. In a ninja world, power and potential are highly regarded, so Naruto might be overlooked because his sister seems to have more of that 'special something' at first glance.
Another storyline could involve Naruto's sister being trained more rigorously by the village elders because they see more potential in her. Naruto, feeling neglected, then goes on a self - discovery journey to find his own strength outside the village's traditional training methods. As he grows stronger, his sister realizes the mistake of the elders and tries to make it up to Naruto.