One interesting plotline could be Naruto and Sakura traveling back in time to their early days at the academy. They could use their future knowledge to change certain events, like preventing some of the early hardships they faced. For example, Naruto might stop himself from pulling that first prank that got him in so much trouble, and Sakura could avoid some of her early insecurities.
Another plotline might involve them traveling back to a crucial moment in the ninja war. They could change the outcome of a battle, perhaps by warning their past selves about an ambush or a powerful enemy's weakness. This would not only alter the course of the war but also their relationships with other characters.
A possible plotline could involve Naruto's return after having some sort of spiritual awakening. He returns to the village, and Sakura is the first person he seeks out. Their interactions then lead to a deeper understanding of their feelings for each other. This could involve flashbacks to their past experiences together and how those have shaped their current relationship.
One interesting plotline could be Naruto traveling back in time to his parents' era. He could try to prevent their deaths and change the future of the Hidden Leaf. Another plotline might be Naruto going back to his own early childhood and using his future knowledge to avoid some of the hardships he faced, like the loneliness and the discrimination from the villagers.
One interesting plotline could be Naruto and his friends traveling back in time to prevent a great tragedy that happened in their world. For example, they might go back to stop the destruction of a village.
One interesting plotline could be Naruto and Shikamaru traveling back to the time of the founding of Konoha. They could use their modern - day knowledge and skills to influence the village's formation in a positive way, like introducing new jutsu training methods. Another could be them going back to key battles in the past to change the outcome and save lives that were lost. Maybe they prevent the death of a beloved character, which then has a ripple effect on the future of the ninja world.
One interesting plotline could be Naruto and Kurenai traveling back in time to the founding of Konoha. They could use their modern - day knowledge and skills to influence the village's early development in positive ways, like introducing new training techniques.
One possible plotline could be Naruto and Mikoto traveling back in time and trying to prevent certain tragedies in the Naruto universe. For example, they might work to stop the Uchiha massacre, which would change the course of many characters' lives.
One interesting plotline could be Gohan traveling back in time to prevent certain tragedies. For example, he might go back to stop the death of his father, Goku. This would change the entire course of the Dragon Ball Z story. Another could be Gohan using his knowledge from the future to train his younger self more effectively, leading to a much stronger Gohan at an earlier stage.
A possible plotline is Naruto going back in time and meeting his parents when they were young. He could influence their lives in a positive way, perhaps by helping them become even stronger ninjas. This could also lead to changes in how Naruto was raised and his own development as a ninja.
In some fanfictions, they might time travel to an era where the Quincy were more powerful. Ichigo, being part Quincy, might have to face some difficult decisions regarding his heritage. Orihime would be there to support him, and together they could end up changing the course of history between the Shinigami and the Quincy. This could lead to a completely different world in the present, with new alliances and enmities.
Another plotline could involve a villain traveling back in time to use the Juubi's power in a different era. They could manipulate events to their advantage, like changing the outcome of important battles or influencing key characters to side with them. This would force the heroes to also time - travel to stop the villain's plan.