A plot could revolve around a mysterious jutsu that starts to affect the memories of the villagers. Naruto and Sasuke suspect it has something to do with an old enemy who's come back in a new form. They embark on a journey to find the source and reverse the effects. It would involve a lot of detective - like work and some intense battles along the way.
One idea could be Naruto and Sasuke teaming up to face a new, powerful and ancient threat that even the combined might of the Hidden Villages can't handle easily. They have to use their unique skills and the bond they've reforged as Hokage and his equal.
Perhaps there's a prophecy that only Naruto and Sasuke together can fulfill. It involves traveling to a different dimension where the rules of chakra are completely different. They have to adapt quickly and find a way to bring something back from that dimension that will save the ninja world from an upcoming disaster. This would test their friendship and their abilities to the limit.
A great plot could be that there is a curse that starts to affect all the ninja in the village and only Naruto and Sasuke's combined chakra can break it. They must embark on a journey to find the source of the curse. Along the way, they discover secrets about the past Hokages and how to better lead the village. Or perhaps a plot where Sasuke, who has been away from the village for a long time, returns and is shocked to see Naruto's new Hokage - like leadership style. He decides to challenge Naruto not in a fight but in a contest of who can better protect and improve the village, leading to a series of events that show their different approaches.
Perhaps in the fanfiction, there's a prophecy that only Hokage Naruto and Anbu Sasuke can fulfill together. They have to embark on a dangerous journey outside the village to prevent a great disaster. Along the way, they face many challenges that test their friendship and skills. For instance, they might have to fight against ancient and powerful creatures. This would not only show their combat abilities but also how they support each other in difficult situations.
One idea could be Sasuke leading an Anbu mission while Naruto, as Hokage, has to deal with the political fallout of the mission's actions. For example, if the Anbu under Sasuke's command accidentally cross a border during a pursuit, Naruto has to smooth things over with the neighboring village.
One idea could be Naruto facing a new and powerful enemy that challenges the very foundation of the Hidden Leaf while he's Hokage. He has to use his unique leadership style and ninja skills to protect the village. Another could be Naruto implementing new training programs for the younger ninjas, based on his own experiences growing up.
One idea could be a story where Naruto has to face a new, powerful and mysterious enemy that has the ability to manipulate time. This would put his skills as a Hokage to the ultimate test.
One idea could be Naruto facing a new and mysterious threat from a hidden clan that has long been dormant. They could be trying to undermine the peace he has worked so hard to achieve as the Seventh Hokage.
One idea could be exploring the Shodai Hokage's early days as a ninja, before the founding of the village. Maybe show his training and how he developed his unique skills.
One idea could be Naruto having to deal with a new and powerful enemy while still adjusting to his role as the 5th Hokage. Maybe this enemy has a unique jutsu that can disrupt the village's chakra network. Another idea is Naruto using his new position to reform the shinobi education system in the village. He could introduce new training methods that focus on teamwork and moral values as well as combat skills.
One idea could be Naruto as Hokage facing a new threat that only Hinata's unique skills can help with. For example, a mysterious enemy that can nullify normal ninjutsu, but Hinata's Byakugan - based techniques are effective. Another plot could be a time - travel fanfic where Naruto and Hinata go back in time and have to prevent a disaster that would change the future of the Hidden Leaf Village. They could also explore their relationship in a different era.
One idea could be that Sakura becomes Hokage first. Naruto goes on a long-term mission and during his absence, Sakura steps up and proves herself as a great leader. She implements new medical ninja programs in the village. When Naruto returns, he is proud of her and they work together to make the village even better.