It could be her friends from the present who somehow also get sent to the past with her. Maybe Tomoyo, who could be helpful in creating new outfits for Sakura to blend in with the past's fashion.
There might be some historical figures that become main characters. For instance, if Sakura goes back to a feudal Japan - like time, a samurai could be a key character. The samurai could initially be suspicious of Sakura but then become her ally as they face common threats in that time.
A shy boy who also loves to read and he and Sakura bond over their shared love for books. They might form a study group together and support each other in their academic pursuits.
Well, Sakura is definitely one of the main characters, since it's about her going to the past.
There could be Naruto. Since he's Sakura's friend, he would likely be involved, trying to help her deal with the curse mark. He might use his own powers and experiences to support her.
One of the main characters could be Sakura's mother. Mothers are often intuitive about their children's problems. She could be the one who eventually helps Sakura open up about her self - harm. Then, there might be a new acquaintance in Sakura's life, someone she meets randomly. This person could have had a similar experience in the past and be able to offer unique advice and support to Sakura.
Tomoyo would also be an important character. She would be very worried about Sakura. She might use her skills in making costumes to create some special baby clothes for Sakura. And she would be constantly by Sakura's side, taking care of her and trying to comfort her.
Well, it could be about Sakura going back in time and trying to change certain events that happened in her life. Maybe she wants to fix a mistake or save someone she lost.
Perhaps it's a rival of Sakura's. In many fanfics, there are rivalries, whether it's for power, love, or recognition. If Sakura outmaneuvered this rival in an unfair way, like cheating in a competition for a coveted position or a magical power, the rival would hold a grudge and find it hard to forgive her.
The Akatsuki members would be the main ones. It could include Itachi, who is known for his complex character and powerful abilities. His relationship with Sakura could be an interesting aspect, whether it's one of mutual respect or a more adversarial one.
Sakura's family members could play important roles. Her parents could initially be hesitant about her decision to adopt but later come around and become loving grandparents to the adopted child. Also, there could be other ninja in the village. For example, Hinata could be a character. She might become friends with the adopted child and help Sakura with things like cooking for the child or teaching the child some basic self - defense moves.
Sakura's friends like Naruto and Sasuke could be main characters. They might be the ones trying to find a way to save her. They could be using their skills and powers to look for a cure or a solution.