One common theme is the alteration of destiny. Since Naruto travels through time, he has the chance to change things, especially regarding his relationship with Tsunade. Another theme is the exploration of their relationship in a different context. In the original story, their relationship is one way, but in time - travel fanfics, it can develop in unique ways.
One popular 'tsunade x naruto time travel fanfic' might be 'Naruto's Time - Travel Adventure with Tsunade'. In this kind of fanfic, usually Naruto travels back in time and his relationship with Tsunade develops in new and interesting ways. It often involves them facing challenges together that they didn't encounter in the original story, which makes for a very engaging read.
Often, Orochimaru can be a main antagonist. Since he has his own devious plans in the Naruto universe, in a time - travel scenario, he might oppose Naruto and Tsunade's attempts to change things for the better. He could be trying to use the time - travel chaos to his own advantage, like stealing forbidden jutsu from different eras.
Often, Orochimaru can still be a main antagonist. Even in a time - travel scenario, his thirst for power and immortality doesn't change. He might oppose Naruto and Tsunade's attempts to change the past as it could disrupt his own plans for power.
A Naruto and Tsunade time travel fanfiction can be really interesting. It could involve them going back in time to change certain events in the Naruto universe. Maybe they go back to prevent a great tragedy or to save a beloved character. For example, they might travel back to the time of the Uchiha massacre and try to stop it, which would completely change the course of the story.
In a Naruto and Tsunade time travel fanfic, they might travel to a time when the Uchiha clan was at its peak. Naruto could try to prevent some of the tragedies that befell the clan later. Tsunade, with her strength and wisdom, could help in diplomatic efforts. For example, she could work with the clan leaders to improve relations between the Uchiha and the rest of the village. This would not only change the future for the Uchiha but also for Naruto's own life as he has a deep connection with Sasuke, an Uchiha. And Naruto could learn new jutsu from the powerful Uchiha of that time, further enhancing his own skills.
Their relationship could become more of a mentor - mentee in the past. Tsunade has a lot of knowledge and experience that Naruto could learn from. Since they are in a different time, they would rely on each other more. Naruto would look up to Tsunade even more as she uses her skills to navigate the challenges of the past.
In some 'naruto x tsunade time travel fanfiction', an interesting plot could be that Naruto and Tsunade travel back to a time when the Hidden Leaf Village was just being founded. They have to deal with the primitive and often dangerous situations of that era. Naruto might introduce some future - like ideas to help build the village, while Tsunade uses her medical skills and leadership to gain the trust of the early villagers. It's also possible that they face challenges from other ninja clans who are not so welcoming of their new - fangled ways.
Another plot could be that Tsunade uses her medical knowledge along with Naruto's power to go back in time and heal some of the major wounds the ninja world has suffered. They could go back to the time of the First Hokage and help him build a more peaceful and prosperous ninja world from the start. In this way, they might avoid all the wars and conflicts that followed.
One possible plotline could be that Naruto accidentally travels back in time and lands right in front of Tsunade when she was at a crucial point in her life, like just after the death of her loved ones. Naruto, with his future knowledge, helps her cope and in the process, they grow closer. Another plotline could be that Tsunade is sent to the future where she meets an older and more mature Naruto. They initially clash due to their different outlooks from different times but then gradually fall in love as they understand each other better.