One common theme is redemption. Minato often gets a chance to make up for things he couldn't do in his original timeline. Another theme is the strengthening of the father - son bond. Since Naruto and Minato didn't have much time together in the original story, time travel allows them to form a deeper connection.
If Minato time - travels, it could change a lot. For instance, if he prevents the Nine - Tails attack, Naruto would grow up in a very different environment. He might not be the underdog he was in the original story. Also, if Minato changes things during the Uchiha clan's situation, Sasuke's story would be completely different. Konoha's political situation would also be altered. There would be less animosity between different clans perhaps.
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.
One popular 'naruto x minato time travel fanfiction' is 'Back to the Beginning'. It has an interesting plot where Naruto travels back in time and gets to interact with his father Minato in a whole new way. Another one could be 'Time - Twisted Bonds' which focuses on how their relationship evolves due to the time travel situation.
One interesting plot could be Minato traveling back to prevent the Nine - Tails attack on Konoha. He could use his knowledge of future events to stop Orochimaru from influencing the situation that led to the attack. Another plot might be Minato traveling to a time when the Uchiha clan was on the verge of the coup. With his wisdom and power, he could try to find a peaceful solution and prevent the massacre. Also, he could travel to the time of the First Hokage to learn more about the origin of the ninja world and bring back that knowledge to improve Konoha in his own time.
One interesting plot could be Minato and Naruto going back in time and Minato getting to see Naruto grow up from the start. He could teach Naruto things he didn't get to in the original timeline, like more advanced jutsu. Another plot might involve them changing key events in the past that had a major impact on the future of the ninja world. For example, preventing certain tragedies or battles.
The main characters are obviously Naruto and Minato. Naruto is the protagonist of the Naruto series, a young ninja with the Nine - Tails sealed inside him. Minato is Naruto's father, a very powerful ninja known as the Fourth Hokage. In this time - travel fanfiction, their interactions form the core of the story.
Well, at first it would be very strange. Minato would be confused by this female version of his son. But as they interact more, if fem Naruto shows her familiar Naruto - like spirit, Minato would start to see her as family. He might become very protective of her in the past world, which is different from their normal father - son relationship.
Their relationship could start off rocky. Minato may be distrustful of Sakura's sudden appearance. However, as they face challenges together, like fighting against powerful enemies from the past, they start to rely on each other. Sakura might start to see Minato as a mentor figure, learning from his combat skills. Minato, in turn, could see Sakura as a symbol of the future and be motivated to make the world a better place for her generation. Over time, they could form a deep bond that is part friendship and part a shared sense of purpose.
Naruto would have a huge impact. His combat skills, like the Rasengan and his ability to use shadow clones effectively, would enhance the team's fighting power. He could also bring a sense of fun and camaraderie that might be different from what the team is used to. Just think about how he'd interact with Obito and Rin, probably making them laugh with his goofy antics.