Sakura may feel a sense of betrayal, especially if she thought she had a friendly or at least non - hostile relationship with Itachi. However, as time passes, she could start to understand his motives, or she might fight back even more vehemently depending on how the situation unfolds in the fanfiction.
Sakura could also be confused. She may try to reason with Itachi, asking him why he is doing this. If she trusts him to some extent, she might be more compliant while still expressing her discomfort. She may start to analyze the situation, trying to figure out if there is a hidden meaning or purpose behind his actions.
Itachi might be doing this as a means of restraint to prevent Sakura from interfering in a dangerous situation. He may know that she has a tendency to rush into things without thinking, and this is his way of ensuring she stays put. Another idea is that it could be related to a cultural or ritualistic practice within the context of the fanfiction's world.
It could be a story where Itachi has some sort of ulterior motive for restraining Sakura. Maybe he's trying to protect her in a very unorthodox way. For example, he might be aware of a danger that only he can sense, and by restraining her wrists, he's ensuring she doesn't run into harm's way.
It could be Orochimaru. He's always had an interest in powerful shinobi, and Sakura has shown great potential. Itachi might be roping Sakura's wrists to prevent Orochimaru from getting to her and using her for his evil experiments.
She might be a bit confused at first. After all, Itachi has a very complex and somewhat dark past. But she could also grow to understand her father's perspective as she learns more about Itachi herself.
Sakura might initially be terrified. She would probably try to fight back using her combat skills and medical ninjutsu to defend herself. Since she is a strong - willed character, she won't go down without a fight.
Fanfiction is fictional stories written by fans. In this case, it might be about a scenario where Itachi pins Sakura's wrists. It could be part of an action - filled, or perhaps a more complex and dramatic story within the fan - created world of the relevant anime or manga.
Sakura would probably be angry at herself for being captured. She's a proud ninja. So she would start looking for weaknesses in Itachi's hold on her. Maybe she would try to engage him in conversation to find out his motives, all the while formulating a plan to break free. She could also try to send out some sort of signal to her comrades if possible.
Sakura would probably be scared at first. But then, being the strong - willed character she is, she might start to talk back to Itachi. She could say something like 'You don't want to do this, Itachi. I know you have your reasons, but this is wrong.' She would try to use her words to defuse the situation.
I'm not sure if it's a particularly popular type. There are so many different kinds of Naruto fanfiction out there, focusing on various relationships and scenarios. While the idea of Itachi and Sakura interacting in this way might be interesting to some, it may not be as widespread as other more common pairings or plotlines.
Sakura would probably be initially terrified. She would try to use her medical ninjutsu skills to defend herself or at least slow Itachi down. If she realizes she can't overpower him physically, she might try to talk to him, asking him why he's doing this.