There could also be a mentor - like character. Since Sakura has this new situation with the broken seal, she may need someone with more knowledge and experience to guide her. This could be an older wizard or a powerful being who has some connection to the seal or the power that was released. They would play a crucial role in Sakura's journey to understand and control what has happened.
Her friends would probably be main characters too. They would likely be involved in helping Sakura deal with the consequences of the broken seal. For example, if she starts to lose control of her new powers, her friends might try to calm her down or find a solution. Also, if there are new threats because of the broken seal, her friends could be there to fight alongside her.
Sakura herself would be a main character for sure, as the whole story seems to revolve around her and the breaking of her seal.
The breaking of Sakura's seal in the fanfic could be the start of an epic adventure. She might have to go on a journey to find a way to control the new power or to reseal whatever was released. Along the way, she could meet new characters, both good and bad. She may also have to face her own inner demons as the power might be changing her in ways she doesn't fully understand yet. This could be a story of self - discovery and growth for Sakura.
Sakura for sure. And then it might be Deidara. His love for art and his explosive personality would be really funny when paired with Sakura. Also, Sasori could be in it. His puppet - like self and Sakura's medical knowledge could lead to some really strange and humorous interactions. For example, Sakura might mistake Sasori's puppet parts for real injuries and try to 'heal' them.
Obviously, Sakura herself would be the main character. But Naruto and Sasuke would also be important characters as they are part of Team 7. Kakashi would also be there as the team's sensei. In a sakura centric fanfic, though, Sakura's relationships with them would be explored more deeply. For example, her friendship with Naruto might be shown to have new dimensions, and her rivalry - turned - friendship with Sasuke could be further developed.
Since it's a 'sakura memory seal fanfiction', it might have a main character who is on a quest to understand the mystery of the memory seal. There could also be an antagonist, perhaps someone who wants to use the memory seal for evil purposes. There could be a sidekick character as well, like a small spirit that lives among the sakura trees and helps the main character on their journey.
Obviously, Sasuke would be affected. Since it's a Sasusaku - related fanfic, any change in Sakura would impact their relationship. He might have to adjust to a more powerful Sakura, or he could be worried about the consequences of the seal breaking.
Naruto could also be involved in interactions with evil Sakura. Naruto, being the protagonist, would likely try to understand why she has turned evil and might attempt to bring her back to the good side. Their interactions could be full of tension and emotional moments.
Definitely some of the Akatsuki members. Itachi could be one. He is a complex character with his own motives. His presence could add a lot of mystery to the story as Sakura might try to figure out his true intentions. Another could be Deidara. His explosive personality and love for destruction could create some intense confrontations with Sakura.
Obviously, Sakura would be one of the main characters. And the members of the Akatsuki would also be important. For example, characters like Itachi or Pain might play significant roles as they are key figures in the Akatsuki. They could be mentors or antagonists to Sakura depending on how the story is written.
Obviously, Naruto and Sakura would be the main characters. Naruto is the one who is 'over' Sakura, so his transformation in terms of his feelings towards her would be a central aspect. Sakura, too, would play a crucial role as the object of his former affections and as someone who might react to his new stance.
Well, Karin is for sure a main character as she is taking over Sakura's position. Sakura, although being replaced, still has an important role as the benchmark for Karin's replacement. Then, other characters in their shared universe who interact with either of them could be main characters too. For instance, Naruto could be involved, seeing as he is friends with Sakura and may have some sort of reaction to Karin replacing her. Also, characters from their respective teams or groups might be main characters as they would be affected by this replacement.