Perhaps Sakura's sister turned criminal due to a misunderstanding. Maybe she was framed for a crime she didn't commit and in her attempt to clear her name, she had to do some illegal things. In the fanfiction, it could be about Sakura believing in her sister's innocence from the start and Naruto joining her in the search for the truth.
One idea could be that Sakura's sister is a criminal because she was brainwashed by a powerful enemy. She might be forced to carry out heinous acts against the Hidden Leaf Village. The fanfiction could then focus on Naruto and Sakura trying to rescue her and break the brainwashing.
Another possibility is that Sakura's sister was born with a special power that was feared by the village. As a result, she was driven to a life of crime. The fanfiction could explore how Naruto and Sakura struggle to convince the village to accept her sister and help her use her power for good.
Jealousy could be a motivation. If she always felt overshadowed by Sakura, she might turn to criminal activities to gain power and attention. For example, she could steal important ninja scrolls to learn powerful jutsus quickly.
Obviously, Ino and her criminal sister are the main characters. Ino, being a strong - willed kunoichi, is likely to play a central role in the story.
Perhaps the fanfiction focuses on the backstory of Ino's sister. How she became a criminal? It could be due to being influenced by some dark forces in the shinobi world. Ino then has to dig deep into her sister's past to understand her actions and save her from further wrongdoings.
One plot idea could be that Sakura discovers her relation to Deidara later in life. This could lead to a conflict within herself as she has to reconcile her loyalty to her friends in Konoha with her new - found family connection to a former enemy. Another idea is that Deidara, knowing she is his sister, tries to protect her during battles without revealing their relationship at first.
One idea could be that they discover their relation after a long time. For example, Naruto has always felt a special bond with Sakura, and when they find out they're siblings, it adds a whole new layer to their relationship. Naruto might be more protective of Sakura in a different way than before.
Yes, there might be such fanfiction. In the Naruto fan community, fans often create various imaginative scenarios. Given the popularity of the characters Sakura and Obito, it's not unlikely that someone has written a fanfic where Sakura is Obito's sister. This could open up new storylines and character relationships, exploring different aspects of their personalities and how they interact within this new family dynamic.
Maybe Ash gets lost in the Naruto world and Sakura finds him. At first, she's suspicious, but as she learns about his journey with Pokemon, she decides to help him find a way back. Along the way, they exchange knowledge. Ash teaches her about different Pokemon types, and Sakura shows him some new ninja techniques.
Well, one idea could be exploring how a criminal family within the Naruto universe might have unique jutsu or abilities that are used for illegal activities. For example, they could have a jutsu that allows them to steal chakra undetected.
One idea could be a crossover where Naruto characters are wrongly accused of crimes in the RWBY universe. For example, Naruto could be framed for stealing Dust in Vale. The story could then focus on him proving his innocence while also learning about the unique aspects of the RWBY world.
One idea could be a time - travel fanfiction where Sakura somehow travels back in time and meets Kushina. Kushina could mistake Sakura for a future friend of Naruto's and start to train her in some of her unique Uzumaki techniques. Meanwhile, Naruto is left wondering how Sakura disappeared and tries to find a way to bring her back.