There are many potential plot twists. For instance, the time - traveler might discover that the 100 Years War in the Fate universe is part of a much larger, hidden conflict between different supernatural forces. Their time travel was actually orchestrated by one of these forces to tip the balance in the war. As they try to figure out their role and what's really going on, they could befriend or oppose various characters from the war era. This could lead to complex relationships and a web of events that completely change the nature of the story, as they struggle to find their place in this strange, time - warped version of the 100 Years War.
A really interesting plot twist could be that the time travel is not actually what it seems. In the Fate fanfiction of the 100 Years War, it could be a magical illusion created by a powerful mage on either side. So, the 'time - traveler' is actually just a pawn in a larger magical scheme. This could lead to a lot of confusion and misdirection in the story. Also, the time - traveler could accidentally change the course of the war in a way that benefits the wrong side from their perspective, creating a moral dilemma for them.
In Fate fanfiction with time travel during the 100 Years War, it's important to consider the rules of time travel in the Fate universe. If it's a type of time travel where changes are allowed, then a time - traveler could potentially bring modern weapons or knowledge. This could give an unfair advantage to one side. However, if it's a more 'fixed - timeline' type of time travel, the traveler might be forced to just observe and their presence could still have an impact on the psychological state of the soldiers, which in turn could affect the war in unexpected ways.
One possible plot twist could be Naruto changing the outcome of a major battle. For example, in the Second Shinobi War, there were many crucial battles. Naruto might use his future knowledge to prevent the death of a key ninja. This would have a huge impact on the future of the ninja world as that ninja could then go on to change other events.
Maybe in the fanfiction, the time travel causes a mix - up of jutsu knowledge. A character from the future accidentally gives the wrong kind of jutsu knowledge to a past - self or another character during the Fourth Shinobi War. This then leads to new and unforeseen strategies being developed by the shinobi, either for good or bad, depending on how it's used. It could completely change the power dynamics in the war.
In many Naruto time travel Third War fanfictions, a great plot twist is when Naruto's time - traveling disrupts the chakra flow of the world during the Third War. This causes unexpected things to happen, like certain kekkei genkai to mutate or new forms of ninjutsu to emerge spontaneously. It could also be that Naruto, while trying to prevent a certain tragedy, actually causes a different and more severe one, leading to a completely different future. This forces him to find a way to fix his mistake while in the middle of a war - torn world.
A plot twist could be that Medusa is actually an undercover agent sent to the Naruto world to steal secrets, but she falls in love with Naruto instead. This would create a conflict between her original mission and her new - found feelings.
A possible plot twist in this fanfiction might be that Naruto's new status as the jinchuriki of Saiken attracts a new group of enemies who are specifically after the power of the Six - Tails. Also, there could be a situation where Naruto's friends start to fear him because of Saiken's power, thinking he might lose control. And perhaps there is a hidden prophecy that only Naruto as the jinchuriki of Saiken can fulfill, which leads to a whole new adventure and set of challenges for him.
A plot twist might be that Harry's past enemies from the wizarding world somehow find a way to cross over into the Naruto world. This would force Shikaku and Harry to team up not only with the ninjas but also with some of Harry's old friends from Hogwarts. It would create a really chaotic and interesting situation where two different worlds' powers and skills collide.
A potential plot twist could be that Zabuza has a hidden agenda for allowing Naruto to join him. Maybe he plans to use Naruto as a pawn against the Hidden Leaf Village, which would create a huge moral dilemma for Naruto.
A potential plot twist could be that Roger is actually a time - traveler. He came from the past to meet Luffy for a specific purpose, like to prevent a great disaster in the pirate world that only Luffy can help with in the future.
One potential twist could be that Percy is actually undercover for the good guys all along while pretending to join Gaea.