The bijuu are the main characters as they are the focus of the 'goes to Yuki Academy' part. However, depending on how the story unfolds, there might be some side characters like the academy's janitor who has some secret knowledge about the bijuu and ends up helping them in unexpected ways, but still, the bijuu are the central figures.
Well, in this fanfiction, the bijuu could cause chaos at Yuki Academy. Maybe they struggle to adapt to the academic environment.
Obviously Naruto is one of the main characters as the title implies his role as the master of bijuu. Other characters could include his friends like Sasuke and Sakura. Since it's related to bijuu, the jinchuriki of other bijuu might also be important characters, like Killer Bee who was the host of the Eight - Tails.
Well, Naruto is the obvious main character. However, depending on the plot, characters like Kakashi could be involved as well. He could be guiding Naruto in handling his godlike powers. And the villains in the fanfiction could also be main characters in a sense, as they would be the ones creating challenges for Naruto in his new state with the godlike bijuu powers.
In some popular 'naruto female bijuu fanfiction', characters like Hinata can often be reimagined as a female jinchuriki. Another common main character is an original female character created specifically for the fanfiction. Sometimes, Sakura is also given the role of a jinchuriki in certain fanfictions.
Obviously, Ash is one of the main characters. Pikachu would also be there with him, as his loyal partner. There might be some new characters created specifically for this fanfiction, like a strict but fair teacher at the academy or a friendly rival who Ash meets on his first day.
Sasuke could also be a main character. His quest for power and his unique abilities might make him interested in the artificial bijuu. He could either be trying to use them for his own goals or be against their existence, depending on the plot of the fanfiction.
The two main characters are Naruto and Princess Yuki. Naruto is a very energetic and determined ninja. He has a big heart and is always ready to fight for what is right. Princess Yuki is probably a character with a lot of grace and poise. She may have diplomatic skills and be in charge of the well - being of her people. Their interactions form the core of the fanfiction.
Maybe there's a rogue ninja who has developed a new and dangerous jutsu that can counter Naruto's powers. This ninja wants to prove himself as the strongest by defeating Naruto and taking over the bijuu's power. He might be jealous of Naruto's newfound status and the respect he gets from the other ninjas.
The main character is Naruto, of course. In addition, there may be a female character who is a skilled horse rider and a good shot. She could initially be skeptical of Naruto but later become his ally. And there might be an old wise man in the Western town who helps Naruto understand the ways of the West and gives him advice on how to use his skills in this new environment.
Obviously Naruto is one of the main characters as the title 'naruto goes blind fanfiction' implies. His friends like Sasuke and Sakura are also likely to be main characters. They play important roles in Naruto's life, especially when he's dealing with his blindness. They could be his support system or even be part of the conflict in some cases.