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.
She would become more stealthy and less impulsive. Since ANBU work requires a lot of secrecy and patience, Itachi's training would force her to change her approach. She might start thinking more strategically and be less likely to jump into a fight without a plan. This could completely transform her from the somewhat brash character she was before.
One possible plot could be a story where Sakura, Itachi, and Shisui are all part of the ANBU. Itachi and Shisui could be mentoring Sakura in the ways of the ANBU. They might go on a dangerous mission together, facing powerful enemies. Shisui could use his unique abilities like Kotoamatsukami to gain an advantage, while Itachi's Sharingan and combat skills are also crucial. Sakura, with her medical ninjutsu and growing combat skills, could prove to be a valuable asset in the team.
It could be about Itachi training Sakura in various skills, like ninja techniques. Maybe Itachi imparts his knowledge of genjutsu or combat strategies to Sakura.
You can try looking on fanfiction websites like FanFiction.net or Archive of Our Own. They have a large collection of Naruto - related fanfics, and there's a good chance you'll find the 'itachi trains sakura' one there.
One possible plot could be that Itachi and Shisui are on a mission in the ANBU and they cross paths with Sakura who is also on a mission related to a medical emergency in a war - torn area. They initially have some misunderstandings as Sakura is not used to the ANBU's way of doing things, but eventually they work together. Itachi and Shisui use their combat skills while Sakura uses her medical ninjutsu to save a village from a hidden enemy's attack.
One plot idea could be that Sakura, as a medic in the Anbu, is assigned to a mission with Itachi. They initially have some misunderstandings due to their different personalities. Sakura is outspoken and Itachi is more reserved. But as the mission progresses, they start to understand and respect each other's skills. Sakura learns from Itachi's stealth and combat techniques, while Itachi comes to appreciate Sakura's medical knowledge and her tenacity in difficult situations.
A plot could involve Sakura getting caught in a political intrigue within the Anbu that Itachi is also a part of. Itachi tries to keep Sakura out of it, but she's determined to uncover the truth. This leads to a series of events where they have to rely on each other's strengths and overcome their own weaknesses.
She probably changes in her mindset. Itachi's influence might make her think more strategically. Instead of just relying on brute force or basic medical ninjutsu, she could start to analyze situations better and come up with more effective solutions. For instance, she might learn from Itachi how to anticipate an opponent's moves based on their body language and chakra flow.
Sakura would likely develop her combat skills further. In the ANBU environment, she would face more dangerous opponents, which would force her to become more strategic. Itachi, already a complex character, might show more of his internal struggle between his loyalty to the village and his love for his family. Shisui could develop in terms of his leadership skills, as he and Itachi might lead Sakura in missions. He could also become more jaded as he faces the darker side of the ninja world.
The main characters are obviously Itachi and Sakura. Itachi is a complex character from the Uchiha clan known for his powerful Sharingan abilities. Sakura, on the other hand, is a skilled kunoichi who has grown in her medical and combat abilities. In this fanfiction, they are usually placed in the context of the ANBU, which is a special and secretive part of the ninja world.