Maybe Naruto goes to a world where there are no ninjas but a strict caste system. He then tries to break the caste boundaries and fight for equality, using his ninja way of believing in everyone's potential.
One idea could be that Naruto arrives in a world full of magic. He tries to understand and master the new magic system using his ninja skills as a base. For example, he might find that his chakra control can be adapted to control magical energy in a unique way.
Well, perhaps in the other universe, Harry finds that Voldemort is actually a hero. This would completely flip his understanding of good and evil. He could also meet alternate versions of his friends. For example, Ron could be a super - intelligent wizard instead of the more laid - back character he is in the original universe. And Hermione might be a powerful athlete rather than a bookworm. This would create a lot of interesting interactions and character development for Harry.
One idea could be Naruto arriving in a world full of magic, and he has to learn to combine his chakra skills with magic. For example, he might use his Rasengan with a magical spell to create a super - powerful attack.
One idea could be that the characters are transported to a world where the Grimm are super intelligent and have formed their own society. The RWBY team has to find a way to communicate and make peace with them.
Well, perhaps a group of outcast ninjas who have been mistreated by the major villages join forces. They develop a new and powerful fighting style that no one has seen before. They start by infiltrating the smaller villages, taking them over quietly, and then use the resources and manpower of those villages to launch a full - scale attack on the larger ones, aiming to take over the entire Naruto world.
One idea could be Naruto as a street artist in a modern city. He uses his ninja skills to create amazing and fast art, like how he throws kunai, he throws paintbrushes to make unique patterns. Another is having Sasuke as a corporate spy, using his Sharingan to gather information secretly in high - tech business meetings.
Perhaps Naruto gets influenced by a dark and ancient power. He starts to see the ninja world as corrupt and decides to reshape it according to his own dark vision. He could form his own army of outcasts and fight against the established ninja villages.
One idea could be that Naruto characters are transported to the World of Warcraft universe. They could form alliances with different races like the Night Elves, with Naruto's ability to befriend others coming in handy. Another could be that the chakra system in Naruto somehow interacts with the magic in WoW, creating new and powerful spells.
An interesting plot idea for Naruto fanfic might be to focus on the life of a minor character. For instance, what if we told the story of a genin who never made it to be a chunin but still had a significant impact on the village in some other way? Or a story where all the ninja abilities are suddenly switched among the characters, and they have to adapt to these new powers while still facing their usual enemies. This could lead to some really fun and unexpected character interactions.
A cool plot could be that Naruto is turned into a small child again, but he still has all his memories. He has to re - live parts of his life, but this time, he can use his knowledge to change things for the better. For example, he could befriend Sasuke much earlier and prevent him from going to Orochimaru. This would be a really interesting take on his character development and his relationships.
Another plot could be that Hermione goes back in time and ends up changing the relationships between the main characters. Maybe she accidentally causes a rift between Harry and Ron, and then has to figure out how to fix it while also dealing with the overarching threat of Voldemort in that time period.