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.
Tsunade would probably be very suspicious at first. Naruto suddenly appearing from the future? It's not something that happens every day. She might think it's some kind of enemy's trick or a genjutsu.
One common theme is redemption. They might go back in time to give a character a second chance at a better life. Another theme could be the exploration of different relationships. For instance, how Naruto and Tsunade's relationship changes when they are in a different time period.
Often, it could be the same antagonists from the original Naruto series but in a different context. For example, Orochimaru might still be an antagonist if he tries to use the time - travel situation to his advantage, like getting his hands on some ancient forbidden jutsu.
One common theme is redemption. Tsunade often travels back to correct her past mistakes or the mistakes of others in the Naruto world. For example, she might try to save a character who died prematurely in the original story.
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.
Well, in some fanfictions, Naruto and Tsunade time travel and end up changing the power dynamics in the ninja world. Maybe they help a small village become a major power by introducing modern ninja concepts. Also, they could time travel to a period when the Akatsuki was first formed and try to disband it before it causes too much chaos.
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.
One interesting plot could be that Naruto and Tsunade travel back in time to the founding of Konoha. They could use their modern - day knowledge and skills to change certain events for the better. For example, Naruto might be able to prevent some of the early conflicts within the village using his understanding of unity. Tsunade could use her medical skills to save lives that were lost in the past, which in turn could have a huge impact on the future of Konoha.
In a time - travel scenario, Naruto's exuberant personality could initially shock Tsunade. But as they spend more time together, Naruto's determination to protect might make Tsunade see him in a new light. His growth and understanding of the past could also intrigue her. Maybe they'd start off as comrades trying to fix things in the past, and slowly feelings would develop as they rely on each other more and more.