Naruto himself is often a popular character in such fanfictions. Since he has a strong connection with the bijuus, especially Kurama, his time - traveling adventures can create really interesting stories. Another popular character is Sasuke. His power and his complex relationship with Naruto can add depth to time travel plots.
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.
One interesting plot could be the main character traveling back in time and preventing the initial capture of the bijuus. This would completely change the power dynamics in the Naruto world. Another could be a character using time travel to team up with past jinchuriki to fight a new, greater threat.
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.
It could be an ancient sage. In Naruto lore, there are sages who have had a great influence on the world. An ancient sage could be the one who created or fathered the bijuu. Maybe he had some great power and knowledge that allowed him to bring the bijuu into existence.
Naruto himself is often a popular choice. Fans like to see him go back in time and use his future knowledge and skills to change things. Sasuke is also quite popular. His complex backstory and powerful abilities make for interesting time - travel scenarios. Another popular character is Kakashi. He has a lot of mystery and potential for development in time - travel stories, especially with his Sharingan and his relationship with Obito.
There's a character named Akira in many Naruto time travel OC fanfictions. Akira is usually an intelligent and strong - willed ninja who travels back to the time of the founding of the ninja villages. He tries to correct the mistakes made in the past that led to future conflicts. Then there's Yuki, a female OC. She travels back to the time when Naruto was a child and becomes his mentor, teaching him some advanced techniques that were lost in her time.
Sasuke is also a popular character in these fanfictions. In time travel scenarios, he might either be an ally or an antagonist to Naruto depending on the plot. For example, if Naruto's time travel changes Sasuke's past in a way he doesn't like, Sasuke could oppose Naruto.
Naruto himself is often a central and popular character. Since it's a time - travel story about him, his antics in the past are what drive a lot of the humor. His naivete in the past combined with his future knowledge can lead to some really funny situations.
Sasuke is also popular. His brooding nature and his own complex journey make him a great character to include in time - travel plots. Fans like to see how he might be influenced by a time - traveler, especially if it affects his path towards revenge or redemption.