In this fanfiction, it could be that they are sent back in time by an ancient power. When they arrive in the past, they are met with a version of themselves that are much more naive. The kiss might happen as a form of comfort between them, especially when they see the challenges that lie ahead in this different time. This event could set off a chain of events where they have to balance their relationship, their mission to return to their own time, and their desire to fix the past.
Maybe the time travel is caused by a mysterious time - space ninjutsu. In the past, Naruto and Sasuke find themselves in a world where their actions can have a huge impact on the future. The kiss could be a spontaneous reaction to the realization that they are the only ones who truly understand each other across time. As the story progresses, they might try to prevent certain tragedies from happening in the past, all while dealing with their new - found and complicated relationship.
In this type of fanfiction, the time travel might be a result of a forbidden scroll or an experiment by a rogue ninja. When Naruto and Sasuke go back in time, their relationship is different from what it was in their original time. The kiss could be a turning point where they start to understand their feelings for each other on a deeper level, perhaps realizing that their bond is stronger than just friendship or rivalry.
One possible plot twist could be that Sasuke, upon traveling to the past, accidentally changes a small event that has huge ramifications in the future. For example, he might prevent a key encounter that led to a character's development, and as a result, the entire power balance in the ninja world is altered. Another twist could be that Sasuke's presence in the past is somehow detected by an ancient and powerful force, which then tries to either use him or destroy him. Or perhaps, Sasuke discovers that his own past self is not as he remembered, and there are hidden motives or secrets that he was unaware of before.
In this fanfiction, it might be that Sasuke got injured during the mission. Naruto, in a moment of relief after saving Sasuke's life, kissed him. This act could be the start of a new dynamic in their relationship, where they have to confront their feelings for each other while still completing the mission at hand.
One interesting plot twist could be Naruto changing the past in a way that completely alters the future relationships. For example, if he manages to prevent certain tragedies from happening to his friends' families, it could lead to very different dynamics. Maybe Sasuke's family wouldn't be massacred, and Sasuke would grow up in a completely different environment, which might change his entire attitude towards the village and Naruto himself. This could lead to a whole new set of adventures and challenges for Naruto as he tries to adapt to this new timeline.
In such a fanfiction, they might try to prevent some of the tragedies that occurred in their own time. For example, Naruto could stop the Uchiha massacre, saving Sasuke's family and potentially changing Sasuke's entire path. Sasuke, on the other hand, might use his knowledge to help the ninja world avoid future wars. They could also meet their younger selves and impart wisdom or skills that they learned in their original timeline.
Maybe they travel back to their early days at the ninja academy. Naruto, who now has all his future knowledge, tries to befriend Sasuke in a different way. But Sasuke, being suspicious, thinks Naruto has some ulterior motive. This leads to a whole new set of comical and at the same time tense interactions between them as they both have to deal with their past selves and the changes they want to make.
One possible plot twist could be Naruto changing the past in a way that completely alters the future relationships. For example, if he prevents a certain event that led to a character's death, it could change the whole dynamic among the characters. Another twist could be that Naruto discovers that the past is not as simple as he thought, and there are hidden forces at work that he didn't know about in his original timeline.
One possible plot development could be that Lily initially feels shocked and confused. She might start to question her relationship with James, especially if she has some unacknowledged feelings for him. This event could also cause a rift in her friendship with Sirius, as she may feel betrayed that he didn't tell her about his relationship with James. It could lead to a series of confrontations and emotional outbursts among the three of them, forcing them to re - evaluate their relationships and their own identities within their group.
A possible plot could be that Naruto and Kushina are sent back in time due to a powerful jutsu gone wrong. Once in the past, they decide to prevent the Nine - Tails attack on Konoha. Kushina, with her knowledge of sealing techniques and Naruto's combat skills, could work together to stop the masked man who released the Nine - Tails. This would save many lives and change the future for the better.
One possible plot could be that Naruto and Mito travel back in time to the founding days of the Hidden Leaf. They could use their modern - day knowledge and skills to help shape the village in new ways. For example, Naruto might introduce some of his jutsu training methods, which could enhance the abilities of the early shinobi. Mito, with her knowledge of sealing techniques, could also contribute to strengthening the village's defenses. They could also interact with the early founders like Hashirama and Tobirama, changing the course of history in small but significant ways.