She might feel guilty. Since they are siblings, she could be aware of Naruto's neglect and try to make it up to him in small ways, like sharing her food or secretly leaving him little gifts.
In many fanfictions where Naruto discovers he has a sister, it often changes the entire dynamic of his story. It could give him a new sense of family and belonging that he lacked growing up. Maybe this sister was hidden away for some reason, like to protect her from Naruto's jinchuriki status bringing danger to her. This new relationship can also influence how Naruto approaches his ninja goals and his relationships with his friends.
One possible plot could be that Naruto's little sister is also a ninja in training. She might struggle with the same kind of ostracism Naruto faced because of the Nine - Tails inside him. However, she could also be a source of great support for Naruto, helping him through his toughest times and together they could train to become stronger. Maybe she has a unique ninja ability that even Naruto is in awe of.
Well, perhaps the story could be about Naruto finding out he has a sister who was hidden away for her own safety. Maybe she has some unique powers that the villains are after, and Naruto has to protect her while also learning about his family's past.
No. Incestuous relationships are generally not considered acceptable in most fanfiction communities. The Naruto series promotes positive values and family bonds that are normal and healthy. Having such a plot goes against the general moral and ethical standards that the Naruto fanfiction community typically adheres to.
The baby sister could change Naruto in some ways. He might become more responsible and less reckless. He would have to think about her well - being all the time. For example, he might not take on as many dangerous missions so that he can be around to protect her. And as she grows up, she could also inspire Naruto to strive for a better future for the Hidden Leaf Village, not just for himself but for her as well.
She could be involved in the Akatsuki plot in some way. In the fanfiction, she might have been sent on a mission that led her to cross paths with the Akatsuki members. This could create a whole new storyline where Naruto has to rescue his sister from the clutches of the Akatsuki, adding more depth to the Naruto universe.
The Akatsuki could be potential enemies. They might see Naruto's little sister as a way to get to Naruto. Maybe they think they can use her as a hostage or extract some information from her about Naruto or the Nine - Tails. Another enemy could be some of the rogue ninja who are after the bounty on Naruto's head and see his sister as an easy target to get to him.
Perhaps the main antagonist is a dark figure from within Konoha itself. This person doesn't want Naruto's family to be reunited because it could expose some dark secrets about their own actions in the past. They would do anything to keep the sister hidden and Naruto in the dark, even if it means causing harm to both of them.
In the Naruto series, Naruto doesn't have a biological sister in the original story. So in this fanfiction, the author probably creates a new character to be his sister. It could be an original character with unique abilities and a complex backstory that leads to the situation where Naruto dies by her hand.