In some fanfictions, other important characters from the original series like Hermione Granger or Ron Weasley could also be involved. They might help the founders understand the modern world or play a role in the events that unfold during the time - traveling escapades. For example, Hermione's vast knowledge of magic could be useful in deciphering ancient spells that the founders use.
Perhaps a plot where the founders travel back in time to their own era but with memories of the future. This could lead to them making different decisions in founding Hogwarts, like adding more modern - day safety measures from the start.
Harry Potter himself is often a main character. He might use the time travel necklace to gain more knowledge about his parents or to find a way to defeat Voldemort more effectively.
Ron Weasley can also be a main character in such fanfiction. His loyalty to Harry and his own experiences in the original story can add depth to the time - travel redo plot. He could be the one to provide emotional support or come up with unexpected solutions during the time - travel adventures, even if he may not be as well - versed in the technicalities of magic as Hermione.
Well, Inuyasha and Kagome are almost always involved. They are the central characters of the original series, so it's natural for them to be in time travel fanfictions. Kagome is the one who can travel through the well between her time and Inuyasha's time in the original story, so she often plays a key role in any time - travel - related plot. Inuyasha, with his half - demon powers and his connection to the past of the feudal era, is also crucial.
You'll usually find characters like Godric Gryffindor, Salazar Slytherin, Rowena Ravenclaw, and Helga Hufflepuff. They might be present in spirit or through memories stored in the staff. And then there are the modern - day students who stumble upon the secrets of the staff. They could be original characters created by the fanfiction writer or minor characters from the original books who are given more depth in these stories.
Obviously, the main members of Team Natsu like Natsu, Lucy, Gray, Erza, and Happy are always involved. They are the core of the group and any time travel adventure usually revolves around them.
Naruto is usually one of the main characters. After all, it's a Naruto - centered fanfiction. Sasuke might also be involved as he is a central figure in the Naruto series. Sakura could be there too, given her importance in the original story. And sometimes, characters like Kakashi or Jiraiya might be part of the time - traveling group, as they are strong and experienced ninjas who can add depth to the story.
Neville Longbottom can also be a main character in some 'Harry Potter goes back in time' fanfictions. Given his growth and importance in the original series, in the fanfic, Harry might go back and help Neville become more confident earlier. This could have a significant impact on the fight against Voldemort as Neville could then be an even more powerful ally from an earlier time.
Obviously, Kushina herself is the central character. But often, Minato, her husband, is also involved. Since they are closely related, his actions and reactions to Kushina's time - traveling situation are important parts of the story. Naruto can also be a key character. If Kushina travels to a time when Naruto is already born or in the future, their interactions can be very emotional and drive the plot forward.
Obviously, Harry Potter himself. Then there would be the four founders: Godric Gryffindor, Salazar Slytherin, Rowena Ravenclaw, and Helga Hufflepuff. They could be present in some form, either as ghosts or through memories guiding Harry. Dumbledore might also still play a role, perhaps as a sort of mediator between the modern world and the founders' teachings that Harry is receiving.