It could be that Itachi is being controlled by some dark force or an enemy. He doesn't really want to harm Sakura but has no choice. The fanfic might then focus on Sakura trying to figure out how to break the control on Itachi while also trying to escape from the situation. She could use her medical ninjutsu skills to her advantage in some way.
Perhaps Itachi kidnaps Sakura as a way to send a message to Sasuke. He knows that Sasuke cares about Sakura, and by taking her, he hopes to draw Sasuke out for a confrontation. This would create a lot of tension in the story, with Sakura caught in the middle of their complex relationship.
In such a fanfic, perhaps Itachi kidnaps Sakura for some strategic reason related to the shinobi world. Maybe he thinks Sakura has some knowledge or ability that could be useful to his goals. For example, her medical skills could be crucial for treating someone in his group.
Well, one possibility is that Itachi has some hidden motives. Maybe he believes Sakura has knowledge about something important in the ninja world, like a secret jutsu or information about an enemy. So he kidnaps her to extract that information.
Itachi himself could be seen as the main antagonist in this scenario. After all, he is the one doing the kidnapping.
One possible plot for a 'kisame kidnaps sakura fanfic' could be that Kisame mistakes Sakura for someone else who has wronged his organization. He quickly grabs her and takes her away. Sakura, initially terrified, soon realizes the misunderstanding. She then tries to convince Kisame of his error while also looking for opportunities to free herself. Meanwhile, her friends from the village start a search and rescue mission, leading to a series of intense confrontations between the rescuers and Kisame's allies.
One possible plot could be that Sasuke has some sort of misunderstanding. Maybe he believes Sakura has some information about a threat to Konoha that she's not sharing, so he kidnaps her to force her to talk. Then Sakura tries to convince him that he's wrong while also trying to understand why Sasuke has become so extreme.
One possible plot could be that Itachi, with his mysterious and alluring charm, starts by casually interacting with Sakura in the Hidden Leaf Village. He might save her from a small danger, which makes Sakura curious about him. Then he begins to share his deep thoughts about the ninja world with her, gradually drawing her in with his intelligence and different perspective.
Well, in such a fanfiction, Itachi might kidnap Hinata for various reasons. Maybe he's being controlled by some dark force and needs Hinata for some ritual. Or perhaps he's been misinformed that Hinata has some special power that can help him in his secret mission against the Hidden Leaf Village.
Well, one possibility could be that Itachi has some hidden motive related to the Uchiha clan's secrets. He might think Kakashi knows something crucial. So, he kidnaps him to interrogate him in a secret location.
Well, one possibility could be that Itachi sees potential in Sakura's skills and decides to train her in the ways of the ANBU. He might start with teaching her stealth techniques, like how to move silently and blend into the shadows. This could involve a lot of practical exercises in different terrains.
Maybe Itachi, despite his stoic nature, starts to have an unexpected soft spot for Sakura. He could be secretly protecting her during her missions, which might lead to some tense and mysterious moments as Sakura tries to figure out who her mysterious protector is.