A third plotline could be about their shared family history. They might uncover secrets about their family that have implications for the greater Naruto world. For instance, their family could be related to some ancient power or prophecy, and together they have to figure out how to deal with it. This would bring in elements of adventure and exploration.
Another plotline could involve Tobi protecting Sakura in secret because of their family bond. Maybe there are threats against Sakura and Tobi uses his powers and influence to keep her safe without revealing his identity as her brother at first. This could add a layer of mystery and suspense to the story.
One possible plotline could be the sister's journey to overcome the abuse. Maybe she finds a support system, like a new friend or a kind neighbor, who helps her gain the strength to stand up against the abuser.
With Sasuke, it could be that Sakura's connection to Tobi makes Sasuke view her in a different light. He might be more cautious around her or see her as a potential threat if he thinks Tobi's motives are not pure. Or on the other hand, it could lead to an alliance between them as they try to figure out Tobi's true intentions.
A sakura's sister fanfiction could also focus on their relationship when they were children. Perhaps there was a misunderstanding between them that led to a rift, and the story could be about how they eventually reconcile and grow closer as sisters.
One possible plotline could be the power dynamics within their family. Since Aro is a powerful vampire in the Twilight universe, Bella being his sister might lead to her having unique powers or a special status. Another could be the love triangle situation. If Bella is Aro's sister, how would that affect her relationships with Edward or Jacob? It could add a whole new layer of complexity to the story.
Well, perhaps the story could revolve around the sister's past before becoming a vampire. She might have had a human life full of secrets and unfinished business. In the fanfiction, she could be trying to resolve those while dealing with her new vampiric nature and her relationship with Bella. For example, she might have had a human love interest and now she has to figure out how that fits in with her new existence as a vampire sister to Bella.
One possible plotline could be Naruto's sister having a unique ninja ability that she discovers and uses to help the village. Maybe she has some sort of nature - based power that no one has seen before. For example, the ability to control plants in a way that can heal injured people or trap enemies.
There could be a plotline where Naruto and Sakura discover a hidden part of the academy that holds ancient ninja secrets. They have to work together to unlock the secrets, and along the way, they face various challenges and also grow closer as friends. This could also lead to them learning new powers or techniques that are unique to this hidden part of the academy.
One interesting plotline could be Naruto, now in Sakura's body, using his unique combat knowledge to improve Sakura's fighting skills in a new and unexpected way. For example, he might combine his shadow clone technique with Sakura's brute strength, creating a whole new fighting style.
A really engaging plotline might be where Naruto forces Sakura to participate in a ninja tournament against her will. At first, Sakura is reluctant, but as the tournament progresses, she realizes the importance of stepping out of her comfort zone. She then starts to train hard with Naruto's help, and they both learn new things about themselves and each other. This could also lead to a deeper understanding and respect between them in the story.
One interesting plotline could be Naruto and Sakura being assigned a top - secret mission in the ANBU. They have to infiltrate an enemy organization together. Along the way, they discover new powers within themselves and also deepen their bond as comrades. Maybe Naruto unlocks a new form of his chakra while Sakura refines her medical ninjutsu to be used in combat situations in a more deadly way.