A common plot is that they are sent back in time by some sort of magic or a powerful jutsu gone wrong. Once in the past, they have to find a way to get back. Along the way, they end up changing little things that have a big impact on the future. For example, Naruto might accidentally teach a young ninja a new move that wasn't supposed to exist yet, and Hinata could inspire a young girl to be more assertive, which then changes the social dynamics in the future.
In some fanfictions, they time travel to the era of the First Hokage. There, they learn ancient ninja techniques and use that knowledge to better their own time. Naruto might also use this opportunity to understand more about the origin of chakra and how it was used in the past, while Hinata could gain more confidence by seeing strong female ninjas in that era.
One popular plotline is that Naruto and Hinata travel back to the time when the Uchiha clan was still intact. They try to prevent the massacre from happening, which changes the whole future of the ninja world. Another plotline could be them going back to their childhood days. Hinata gets a chance to be more confident around Naruto earlier, and Naruto realizes Hinata's feelings sooner, leading to a different relationship development.
One popular plotline could be about the challenges they face as new parents. For example, Naruto might struggle to balance his Hokage duties with being a father. Hinata, on the other hand, could be dealing with the pressures of raising a child with such a high - profile father. Another plotline might involve their baby showing some unique ninja abilities from a very young age, and they have to figure out how to train and protect the child at the same time. There could also be a plot where their baby gets kidnapped by an old enemy seeking revenge on Naruto, and they have to embark on a dangerous rescue mission.
A really popular plotline involves Naruto and Mikoto falling in love during their time - travel adventure. Since Naruto is from a different time and has a different perspective, their relationship develops in an interesting way. Also, there are plotlines where they try to change the fate of Sasuke. They want to make sure Sasuke doesn't go down the dark path he did in the original story. This often involves changing the Uchiha clan's standing in the village and fixing the misunderstandings between the clan and the village leaders.
One common plotline is Naruto and Mikoto teaming up to change the future. For example, they might go back in time to prevent certain tragedies in the Naruto universe, like the Uchiha massacre. Another plotline could involve them falling in love during their time - traveling adventures and having to deal with the consequences of their relationship in the altered timelines.
A popular plot in such fanfictions could be a 'what - if' scenario. What if Naruto had a different upbringing? How would that affect his relationships with Sakura and Hinata? Some fanfictions explore this by making Naruto be raised in a different village for a while. Another plotline could be that Sakura discovers a new medical ninjutsu that can enhance the abilities of Naruto and Hinata, and they embark on a journey to perfect this new technique. And then there are those fanfictions where Hinata has a secret power that she reveals during a critical moment when she, Naruto, and Sakura are in danger, changing the course of their adventure.
In many such fanfictions, Naruto and Hinata might be sent back in time through some magical or jutsu - related means. Once they meet their parents, it could be a very emotional moment. Naruto might see his father Minato and mother Kushina, and Hinata could meet her father Hiashi. They could learn a lot about their families' pasts and perhaps even change some things for the better in the timeline.
Another plotline could be Hinata's internal struggle. She's always been in love with Naruto, but when he starts to show interest, she has to overcome her shyness and self - doubt. For example, in some fanfictions, she might doubt if Naruto really loves her or if it's just a passing feeling.
One common theme is redemption. Hinata might go back in time to right the wrongs she or others have committed in the original timeline. Another theme is love. Since Hinata has feelings for Naruto, time travel can be a way to explore a different kind of relationship development, like falling in love all over again in a different context.
The concept of Hinata time traveling allows for a lot of creativity. It gives the author a chance to rewrite parts of the Naruto story with Hinata in a more central and powerful role. For example, she can change events that were unfair to her or her friends in the original story.
One interesting plotline could be Hinata becoming a powerful ninja in her own right and protecting Naruto instead of the other way around. For example, she could master a new and unique jutsu that saves Naruto from a powerful enemy.
One possible plotline could be a story where Naruto has to choose between two versions of Hinata, the original Hinata and a version from an alternate RTN (Road to Ninja) universe. Maybe in this fanfiction, the different Hinatas have unique abilities or personalities that make Naruto's choice more difficult.