Well, his time - travel might create alternate timelines. If he changes a significant event, like preventing a major villain from rising to power in the past, the whole future could be rewritten. There could be new friendships, new enemies, and new power dynamics. The shinobi world as he knew it might cease to exist, or at least be very different.
If Kakashi travels back in time, his actions could have a butterfly effect. For example, if he saves someone who was supposed to die, that person's actions in the future could be completely different. This could lead to changes in alliances, battles, and even the political structure of the village.
One common theme is redemption. Since Kakashi can go back in time, he often tries to make up for past mistakes or prevent tragedies that occurred in the original timeline. For example, he might try to save a character who died before. Another theme is the changing of fates. He can change the destiny of not only himself but also of his friends and the whole village. He can use his knowledge of future events to better prepare for threats.
A cool plot would be Kakashi traveling back to a time during one of the great ninja wars, say the Third Great Ninja War. He could use his knowledge of future jutsu and strategies to turn the tides of battles that were previously lost. He might also be able to save comrades who died in the original timeline, and in the process, change the future of many ninja families.
One great Kakashi Hokage time travel fanfiction is 'Kakashi's Time - Travel Redemption'. In this fic, Kakashi goes back in time and uses his knowledge to prevent some of the tragedies that happened in the original timeline. He focuses on training the younger generation earlier and making strategic changes. It's a really interesting read as it shows a different side of Kakashi's leadership and how he could have changed the course of the Naruto world if given the chance to go back.
In a Sakura and Kakashi time travel fanfiction, they could end up in the past during a major war. Kakashi would be a great asset with his Sharingan and combat skills. Sakura, on the other hand, could help the wounded soldiers. Their presence in the past could change the outcome of the war. For example, they might be able to save some important characters who were supposed to die. This would then lead to a completely different future when they return to their own time.
Another possibility is Naruto traveling back to his own childhood days. He could mentor his younger self, teaching him advanced jutsu and wisdom he's gained over the years. This would make his younger self much stronger much earlier, and might also change how he interacts with Sasuke. For example, he could help his younger self better understand Sasuke's pain and prevent some of their earlier conflicts.
One great 'Naruto Hokage Time Travel Fanfiction' is 'A New Beginning'. It has an interesting plot where Naruto travels back in time and uses his knowledge to change many things in the ninja world. The character development is really well - done, especially how Naruto becomes more cautious and strategic with his second chance at life.
You can have existing characters like Handsome Jack be affected by time travel. For example, he could be sent back to a time when he was just starting his rise to power. This would show a different side of him, perhaps more vulnerable or idealistic before he became the tyrant we know. The Vault Hunters could then interact with this younger Jack and either try to change his future or be influenced by his earlier ideas.
In a time - travel scenario, their relationship could develop in many ways. At first, they might be strictly in a teacher - student type of relationship as they always were. But as they face the challenges of the past together, they could become more like equals. For example, Sakura might come up with a plan to deal with an old - time enemy using her modern - day knowledge, and Kakashi would have to respect her for that. They might also develop a deeper bond of trust as they rely on each other to survive in a strange time. And perhaps, there could be some moments of self - discovery for both of them as they see how they fit into the past and how they've changed from who they used to be.
Naruto is often a common character. Since Naruto has a strong bond with Kakashi, he might be involved in Kakashi's time - traveling adventures. Sasuke could also be there. Their relationship with Kakashi in the original story makes it likely for them to show up. And of course, Guy would be a great addition. His friendly rivalry with Kakashi would add some humor and action to the time - travel scenarios.
I really like the fanfic 'Time - Twisted Bonds'. In this one, Kakashi and Naruto are sent back to a crucial point in the history of the ninja world. It has a lot of action scenes and also delves deep into the relationship between Kakashi and Naruto. It's exciting to see how they use their skills and knowledge to navigate the past.