Obviously, Anakin Skywalker and Revan. Anakin is the one being trained, so he will be a central figure. His growth and development under Revan's tutelage will be a major focus.
There could also be other characters who interact with them. For example, Obi - Wan Kenobi might sense a change in Anakin and try to figure out what's going on. Or Palpatine could become suspicious of Anakin's new training and try to interfere. These secondary characters can add more drama and conflict to the story.
The main characters would surely be Anakin Skywalker and Count Dooku. Anakin is the protagonist in a sense as we would see his development through Dooku's training. Dooku, on the other hand, is the one who imparts his knowledge and skills, and his character would also be explored in terms of his motives for training Anakin.
Well, it could involve Anakin learning unique combat styles from Revan. Maybe Revan imparts his knowledge of the Force, which is different from the traditional Jedi teachings Anakin has received. This could lead Anakin to question some of the Jedi Council's ways.
The main characters would be Naruto and Hiruzen. However, we might also see characters like Kakashi make an appearance. Kakashi could be a bit jealous at first that Hiruzen is taking Naruto under his wing, but then he might see the benefits and offer his own advice to Naruto on the side.
Obviously Naruto would be one of the main characters as the title implies he is being trained. And then, the RWBY characters like Ruby, Weiss, Blake and Yang would also be main characters since they are the ones doing the training.
Obviously, Harry and Merlin are the main characters. Harry is the one being trained, and Merlin is the trainer.
Obviously, Naruto and Asuma would be the main characters. Naruto, the protagonist of the Naruto series, is the one being trained. And Asuma, a respected jonin in the Hidden Leaf Village, is the trainer.
Anakin's mother, Shmi, would likely be a very important character. Since Anakin is not being trained as a Jedi, he would be more focused on his family. Shmi's influence on Anakin would be even greater, and she could play a role in guiding his actions and decisions, especially in relation to the local community on Tatooine.
In addition to Naruto and Anakin, the fanfiction might introduce some Naruto - universe characters into the Star Wars setting. For example, Sasuke could show up. His rivalry with Naruto could translate into some sort of conflict or cooperation in the new universe. And of course, the Sith Lords would be there as the antagonists. They would be interested in Anakin's potential, and Naruto would have to protect his son from their influence.
The main characters would be Anakin Skywalker and Darth Plagueis. Anakin, a powerful Force - sensitive, is the focus of the training. Darth Plagueis, a Sith Lord, brings his knowledge of the dark side of the Force to the table. There may also be other supporting characters like the Jedi who might notice Anakin's change in behavior or Padmé, Anakin's love interest, who could be affected by his new training and the path he is on.
Another possible main character could be Gary. Since Gary has a connection to both Ash and Professor Oak, he could play a role. Maybe he's jealous of Ash getting special training from Oak and tries to interfere or he could also be inspired by Ash's training and start his own journey of improvement. Also, Misty or Brock could be involved as they are Ash's friends and might visit during the training to see how he's doing.