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.
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.
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.
One possible interpretation could be a display of power. Itachi is a very powerful character, and pinning Sakura to the wall might be a way to show his dominance in the fictional scenario. It could also be a moment of shock or conflict, perhaps in a situation where their paths cross in an unexpected and tense way.
I'm not sure specifically about 'itachi pins down and marks sakura' fanfictions being popular. Fanfiction is a vast world, and while there may be stories with such a plot, it's hard to say if they are widely popular without doing a thorough search through fanfiction platforms. There are so many different types of Naruto - related fanfictions that it could easily get lost among the masses.
Well, in the context of fanfiction, 'itachi pins down and marks sakura' could imply a particular scenario within a story. Itachi is a character, and if he's 'pinning down and marking' Sakura, it might be a very specific action related to a plot in the fan - created story. Maybe it's a sign of possession or some kind of significant interaction in the fictional world of the fanfiction.
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.
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.
In the original Naruto storyline, Itachi and Sakura don't have such direct and extreme interactions. This fanfiction clearly takes a departure by creating this intense physical encounter. It adds a new layer of relationship that doesn't exist in the source material.