Obviously, Sakura is one of the main characters since it's about her training hard. There might also be her trainer, who could be an experienced and wise figure guiding her through the training process.
In some sakura trains hard fanfiction, there might be a story where Sakura is training under a strict mentor. The mentor pushes her to her limits, but in the process, Sakura discovers new powers or abilities within herself. For example, she could learn to control a special type of energy she didn't know she had before. This discovery could then lead to her taking on more difficult challenges in her training and ultimately becoming a much stronger character.
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.
One great 'Trains Sakura' fanfiction is 'The Sakura Express'. It's about a magical train journey through a land filled with sakura trees. The story beautifully combines the imagery of the trains and the sakura blossoms, creating a really enchanting world. The characters are well - developed, and you can really feel their emotions as they travel on this special train.
There are some great Anko and Sakura fanfictions out there. One interesting one might be where Anko trains Sakura in some unique ninja skills that Sakura hadn't learned before. It could involve Anko teaching Sakura about the more unorthodox and stealthy aspects of being a ninja. Another could focus on the development of their relationship during the training, perhaps starting as a strict teacher - student dynamic and evolving into a friendship.
It could be an old and wise hermit who lives in the forest. This hermit has seen many things and has a vast knowledge of the skills sakura wants to learn. He guides her with tough love, pushing her to her limits but also providing valuable advice when she's in doubt.
Often, the main characters can be train conductors. They are in charge of the sakura trains and are very knowledgeable about the routes and the special features of these trains. They could be guiding passengers through the beautiful sakura - lined tracks.
One interesting sakura trains fanfiction could be about a magical journey on the sakura - themed train. Maybe the train travels through different dimensions filled with cherry blossoms everywhere. Passengers on the train might have extraordinary adventures, like meeting mythical creatures that only exist in the world of cherry blossoms.
Maybe Naruto trains Sakura in combat. He could teach her some of his unorthodox fighting moves. Since Naruto has faced so many different opponents, he has a wide range of combat experience. He might show Sakura how to better anticipate an opponent's moves and counter them effectively. Sakura, in turn, could use her intelligence to analyze and improve on the techniques Naruto teaches her.
One possible plot could be that Sasori, with his unique skills in puppetry, decides to train Sakura in combat techniques that involve precise movements and control, much like how he controls his puppets. He might see potential in her that others overlook, perhaps her determination and ability to learn quickly.