There are also some fanfictions where Sakura is paired with a completely new character. This character could be from another village or even another dimension. It adds an element of mystery and newness to the story as Sakura has to navigate a relationship with someone she has no prior knowledge of.
Naruto can also be paired with Sakura in these fanfictions. Since they are such close friends in the original, in a reincarnation scenario, their friendship could potentially turn into something more romantic. They could support each other in different ways than in their past lives.
Often, Kakashi is paired with Sakura in these fanfictions. Since he is her teacher, in a badass multi fanfiction, he might take her on special missions where she really shows her skills. Also, Rock Lee could be paired with her. They both have a strong will and in fanfiction, they could team up to take on some really tough opponents. Their relationship can be developed in a more action - packed and interesting way.
Many fanfictions pair Ash, in his reincarnated state, with new characters as well. Sometimes there are powerful Pokémon trainers or even mysterious characters from different dimensions. These new pairings can introduce fresh storylines and dynamics, like the new character guiding Ash through his new, reincarnated journey or being in conflict with him over different goals.
Often, there are also antagonist characters. For instance, a dark sorcerer who wants to use the power of the sakura reincarnation for his own evil purposes. This creates conflict in the story as the protagonists must protect the sakura spirit from being exploited.
In many sakura haruno reverse harem fanfictions, Naruto and Sasuke are almost always there. Naruto's energetic and kind - hearted nature contrasts well with Sasuke's more brooding personality, creating an interesting dynamic around Sakura. Kakashi can also be part of it in some stories, with his mysterious and experienced character adding another layer to the relationships. And then there are often new male characters introduced, like a foreign shinobi who is attracted to Sakura's strength and beauty.
There could be the patients, of course. Each patient might have their own unique backstory and personality. Maybe there's a young patient who is dealing with trauma, and Sakura has to find a way to reach out to them.
In certain 'sakura haruno revenge fanfiction', Orochimaru might be the antagonist. Given his history of using people for his experiments and causing harm, Sakura could decide to take revenge on him, perhaps to stop his evil plans and avenge those who have been affected by his actions.
I don't know for sure, but since it's a fanfiction centered around Sakura Haruno, she is the main focus. However, it may also feature characters who had a major impact on her life. This could include her sensei, like Tsunade, who trained her in medical ninjutsu. There's also a possibility that new characters created specifically for this fanfiction could be main characters as well, but that's just speculation.
In some Sakura Haruno alpha fanfiction, Kakashi could be a significant character. He might act as a mentor to Sakura in her new alpha role. He could guide her in making difficult decisions, like when she has to choose between the safety of the village and the life of a comrade.
One interesting concept could be Sakura being reincarnated in a different ninja village. This would change her whole upbringing and the way she approaches ninjutsu. For example, she might learn different techniques and have different relationships with her new comrades.
Often, Naruto and Sasuke are paired with Sakura Sensei in fanfiction. Since they are the main members of Team 7, many stories involve her interactions with them. For example, she might be teaching them new techniques or helping them deal with personal issues.