In some fanfictions, they may travel to a time when the Sage of Six Paths was alive. Naruto could learn directly from the Sage, and with the Kyuubi by his side, they could gain new powers or insights. This might also lead to a different way of dealing with the tailed beasts in the past, which could have far - reaching consequences for the future.
Perhaps they travel to a time when the Uchiha clan was first being persecuted. Naruto, with the power of the Kyuubi, might be able to change the course of events and save the Uchiha, which would have a huge impact on the entire Naruto world. This could involve Naruto having to convince the village elders of the Uchiha's loyalty and find a way to end the discrimination.
One idea could be Naruto and Kyuubi traveling back to the founding of Konoha. They could use their knowledge of the future to prevent some of the early conflicts and shape Konoha into an even better place from the start.
One idea could be exploring the bond between Naruto and the Kyuubi in a new way. For example, they could have a shared dream where they are in a strange, alternate world and have to work together to find a way back. Another plot could involve Naruto using the Kyuubi's power to save a village from a new, powerful enemy that no one else can defeat. And a third could be about the Kyuubi revealing a long - lost secret about Naruto's family that changes his perspective on his own powers.
One plot idea could be that Naruto and Kyuubi have to work together to stop an ancient evil that is threatening the ninja world. This would require them to fully trust each other and combine their powers in new and unique ways.
One idea could be Naruto exploring the ancient powers of the Kyuubi that were long forgotten. He could discover hidden techniques that only the Kyuubi knew in its long existence.
Perhaps a plot where the female Kyuubi has to take on a human form to protect Naruto from a new, powerful enemy. In the process, they develop feelings for each other while fighting side by side.
Another plot could involve the Kyuubi having a more sentient and family - like relationship with Naruto's family. It could communicate with them in dreams and offer advice or warnings. For example, it might warn them about upcoming threats to the village that Naruto alone might not be able to handle. This would create a unique dynamic where the family has to work with the Kyuubi for the greater good.
One idea could be that the Kyuubi's power somehow interacts with Itachi's Sharingan in a unique way. Maybe Itachi is able to use the Kyuubi's chakra to enhance his genjutsu even further. Another plot could involve Naruto, with the Kyuubi inside him, teaming up with Itachi to face a common enemy that neither could defeat alone. For example, a new powerful Otsutsuki clan member arrives, and their combined skills are needed to save the village.
One idea could be Dark Naruto forming an uneasy alliance with the Kyuubi. They might decide to take on the Hidden Leaf Village together, believing it has wronged Naruto in some way. Naruto could use the Kyuubi's power in a more sinister way than ever before.
Another plot could involve Naruto sharing his Kyuubi cloak powers with his friends. He discovers a way to temporarily transfer some of the cloak's power to them, and they use it to fight a new and powerful enemy that was too strong for them before. This would also strengthen their bonds and teamwork.
A plot could involve Naruto and the Kyuubi being separated by an evil force that wants to control the Kyuubi. Naruto then has to fight his way through various obstacles and enemies to reunite with the Kyuubi and restore their partnership.
A plot could also revolve around Naruto using his Kyuubi - sage powers to bring about peace between the different ninja clans. He could use his unique powers to show that they can all co - exist and work together. By demonstrating the strength that comes from his combination of abilities, he convinces the clans to put aside their differences and collaborate for the betterment of the ninja world.