One possibility is that it's a story set in a fictional and strange world where the laws of nature are different. Pain has a physical form and uses some sort of supernatural means to pin sakura to the wall. The story could then follow sakura's attempts to break free and the consequences of her actions in this unique world.
It could be about a very dark and twisted situation where 'pain' is personified and is physically restraining or harming'sakura' in some way. Maybe it's a psychological horror story where sakura is a victim of some malevolent force represented by 'pain'.
Well, it could be a story about a moment of intense emotion. Maybe Saskue is angry at Sakura for some reason and pins her to the wall in a fit of rage. But then it might turn into a moment of realization for both of them, leading to a deeper understanding of their relationship.
Well, it could be that there are other characters in the background. Maybe there's a character who will come to sakura's rescue. Or perhaps there's a character who is controlling 'pain' and making it do these things to sakura. But from the title, pain and sakura are the most prominent ones.
The main characters are clearly Saskue and Sakura. Saskue is likely to be a complex character in this fanfiction, with his own motives and emotions that lead him to pin Sakura to the wall. Sakura, on the other hand, is probably the recipient of Saskue's actions and will have her own reactions and responses to the situation.
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.
In this fanfiction plot, Sakura could be on a mission to infiltrate Pain's group. However, during her time there, she gets to know Pain on a deeper level. They start to bond over shared experiences of loss and the desire for a better world. Their relationship then becomes a catalyst for change. Sakura tries to bring Pain to the side of good, and together they face many obstacles, both from the Akatsuki and from Konoha, as they try to navigate their new - found love within the context of the Naruto - like world.
Well, one possible plot could be that Sakura, being Pain's sister, tries to change his extreme views. She might use her medical skills to heal the wounds of those affected by Pain's actions in the Hidden Rain Village, and gradually try to bring Pain back to a more peaceful state of mind.
One possible plot could be that Sakura is a new student in high school and Pain is the mysterious loner. They get paired for a project and initially clash due to their different personalities. But as they spend more time together, they start to understand each other. Sakura sees the pain (no pun intended) behind Pain's tough exterior and Pain begins to admire Sakura's determination.
Perhaps Sakura is dealing with family issues. She could be hiding the pain of having a difficult family situation, like an overbearing parent or a family member with an illness. In the fanfiction, she might focus on her school or ninja work to distract herself from her family problems.
In such a fanfiction scenario, it could be a very intense situation. Maybe Kidomaru uses his six arms to physically restrain Sakura. This could lead to a fight where Sakura has to use her medical ninjutsu skills in a more combat - oriented way to break free. For example, she might use her chakra enhanced strength to push Kidomaru's arms away.
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.