Sakura's father would be an important character. His relationship with Sakura's mother is a key part. Also, there could be her friends from her ninja days. They might have trained together or gone on missions as a team.
Obviously, Sakura's mother herself. And her family members like her parents or siblings if they are relevant to the story. They could have influenced her in different ways.
The obvious main character could be the one who ends up in Sakura's body. It could be an original character created by the fanfiction writer.
Maybe Sakura's adoptive parents. Their relationship with Sakura could be explored further in relation to the discovery of her real mother. They might have some secrets of their own regarding how they came to adopt Sakura or they could be in conflict with Sakura as she tries to find her real mother.
There could be the prison guards. Some might be cruel and strict, while others could be more sympathetic. Also, other inmates. Maybe an older, experienced inmate who becomes a mentor - like figure to Sakura.
One possible plot could be that Sakura's real mother was in hiding for some reason, like she was being hunted. Sakura accidentally stumbles upon the truth and has to find a way to protect her mother. Along the way, she learns about her mother's past, her family heritage, and maybe even discovers some long - lost relatives. This could lead to a series of adventures as Sakura tries to keep her mother safe and uncover the whole truth.
Obviously, Sakura would be the main character. Her teammates like Naruto and Sasuke could also be important characters. Their interactions with Sakura would play a big role. Also, her sensei, like Kakashi, might be in the story to guide her. There could be other genin from the village as well, either as friends or rivals.
Obviously, Sakura's sister would be a main character. Sakura herself might also be in it, as well as their friends. There could be a cute animal sidekick too, like a talking cat or a little fairy.
A powerful dragon that guards the school's most precious treasures could be one of the characters. Also, there might be a group of elves who are experts in nature magic and they could be either friends or rivals to Sakura. Another possibility is a half - human, half - phoenix character who has the ability to heal with fire.
Obviously, Sakura is one of the main characters. There could also be a friendly monster teacher to guide her in the new school.
If it's a positive fanfiction, possible themes could be the mother - daughter relationship, like how the mother passes on her wisdom to Sakura.
The two main characters are Sakura and Lemon. Sakura could be a character with her own dreams and aspirations, and her mother Lemon plays a crucial role in either supporting or challenging those dreams. Their relationship, which could be complex and multi - faceted, is what drives the story forward in this fanfiction.