One idea could be that Fuu discovers a hidden power within Naruto's Rinnegan that can open a portal to a different dimension filled with ancient ninja secrets. She then teams up with Naruto to explore this new world and face the challenges within.
Naruto's Rinnegan might allow him to sense Fuu's presence from afar, and Fuu's agility could be enhanced by the Rinnegan's power. For example, if they are in a battle, Naruto could use his Rinnegan to mark the enemies, and Fuu could quickly dart between them, taking them out one by one.
Sasuke could be a rival. He's always been competitive with Naruto, and he might see Fuu as an obstacle in Naruto's path. Also, some of the more arrogant ninja from other villages, like those who look down on Naruto's boisterous nature and Fuu's different style of fighting, could be rivals.
In the fanfiction, their relationship could develop in a very passionate way. Since Naruto is a very emotional and energetic character, and Fuu has her own charm. When they decide to have a child, they would be super excited about the future. However, they would also face difficulties like any couple. There might be times when Naruto's duties as a ninja conflict with his family life, and Fuu would have to be understanding. And vice versa. Through these ups and downs, their love for each other and their child would keep their relationship strong.
I really liked the fanfic 'Naruto and Fuu's Adventure'. It takes them on a journey outside the Hidden Leaf Village. They face various challenges together, and it's really exciting to see how their relationship develops throughout the story.
Naruto would initially struggle with the formalities of a political marriage. But as he spends time with Fuu, he would start to adapt. His character would become more refined in terms of handling political matters. He would learn from Fuu's grace and intelligence. Fuu would also change. She might become more assertive, as she has Naruto by her side. She would be more involved in making decisions for the greater good of both villages. Their characters would grow together, with Naruto's boldness and Fuu's tact combining to create a strong leadership duo for their joined communities.
Naruto's personality would likely become more mature. The responsibility of being in an arranged marriage might make him think more about the future. He would still keep his positive and determined side, but now he has someone else to consider. Fuu's personality could soften. She might start to open up more and show her vulnerable side to Naruto. The marriage could be a catalyst for her to become more trusting and less guarded.
One implication is that he becomes much more powerful. The Rinnegan gives him access to powerful abilities like the Six Paths techniques, which would change the power dynamics in battles in the fanfiction. He could now face stronger enemies more easily.
One great 'Naruto Fuu and Gaara' fanfiction is 'The Bond Beyond Nations'. It focuses on how Fuu and Gaara's relationship develops over time, with Fuu being a character who initially misunderstands Gaara but then comes to see his true self. It has a lot of well - written emotional moments.
Another theme is adventure. Writers love to send them on exciting quests, exploring new places in the Naruto universe or even beyond. For example, they might go on a journey to find a powerful artifact or to save a village from a mysterious threat.