Sakura could be another main character. She might be shocked by Naruto's arrest and start her own investigation. Maybe she teams up with Sasuke, who also has his own complex feelings towards Naruto. Their combined efforts could play an important role in uncovering the truth.
There could be Sasuke. Since Sasuke is Naruto's rival and often involved in the same major story arcs, he might play an important role in this fanfiction. His sharingan abilities could interact with Naruto's newfound speed in some interesting ways, either as an ally or an obstacle depending on the plot.
Rin could also be an important character. She could be the one who takes care of baby Naruto's day - to - day needs, like feeding and cleaning. She could also have a special bond with Naruto, perhaps seeing him as a symbol of hope for the future of the village.
Jiraiya is likely to be a popular character. He was Minato's teacher and has a strong influence on Naruto as well. In a time travel fanfiction, he could provide a lot of wisdom and help in the different situations they encounter. Also, Tsunade could be important. Her leadership skills and medical ninjutsu could be very useful when they are in the past, and she has her own history with both Minato and Naruto's family.
Kushina could be an important character even though she's dead in the original story. In this fanfic, her spirit or memories could play a role in Naruto's upbringing. For example, Minato could tell Naruto stories about Kushina's feisty personality and her love for the village.
Sakura could be a significant character. In the context of Naruto being Minato's son, her relationship with Naruto might change. She could be more in awe of him at first or have different expectations. Also, Sasuke is likely to be a main character. His rivalry with Naruto could take on new dimensions as Naruto has the added legacy of being Minato's son. Their battles and interactions might be more intense and influenced by Naruto's heritage.
Another plot could be that there is a power struggle in the village. Some people want to undermine Minato's leadership and use Naruto as a pawn. They set up a situation where Naruto appears to be a threat, and Minato is pressured into arresting him, but later Minato discovers the truth and has to fight against those who set Naruto up.
Well, in some fanfictions, Naruto might be faster than Minato because he has access to more powerful forms or has trained in unique ways. For example, if Naruto has mastered a new Sage Mode or a super - enhanced version of his Nine - Tails Chakra Mode, it could give him an edge in speed over Minato.
Well, obviously Minato would be one of the main characters since he's in the title. Naruto might also be a main character as it's a Naruto - related fanfic. There could also be other characters like Kushina, Minato's wife, or some of Minato's students or comrades from the Hidden Leaf Village.
Another character that could be important is Jiraiya. Since he was Minato's teacher and Naruto's mentor, he could play a role in the fanfic. Maybe he helps facilitate the meeting between Minato and Naruto, or he has some words of wisdom for both of them during their time together.
Obviously, Minato and Naruto are main characters. Minato is the one who returns, and Naruto is his son, so their relationship is central.