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.
Perhaps the OC is from another village on a diplomatic mission. Ino is assigned to show the OC around Konoha. At first, they have some misunderstandings due to their different village cultures, but as they get to know each other better, they realize they have a lot in common and fall in love.
In a fanfiction, their teamwork could be extraordinary. Ino could use her mind - transfer jutsu to share information with Naruto during a battle. Naruto, being the powerful ninja he is, could then act on that information quickly. For instance, if they are facing an enemy with hidden traps, Ino could transfer the knowledge of the trap locations to Naruto, and he could use his speed and strength to avoid them and attack the enemy from a safe position.
A lot of Ino Yamanaka fanfictions focus on her role in the Hidden Leaf Village. This includes her participation in village - wide events, her loyalty to the village, and how she helps in protecting it. Also, her rivalry - turned - friendship with Sakura is a popular theme that many fanfictions play around with.
In naruto yamanaka fanfiction, a major theme is her role within the village. Is she an underappreciated asset? Writers often explore this. Another common theme is her connection to the spiritual side of the Naruto world. Her clan's abilities are related to the mind and spirit, and fanfictions may expand on how she delves deeper into this aspect. Love and romance can also be a theme, whether it's a budding relationship with a fellow ninja or an unrequited love story that adds an emotional depth to her character.
Another theme is family and clan loyalty. OCs in Yamanaka fanfiction often have to navigate their place within the clan, and this involves dealing with family expectations and loyalty to the clan. For example, they might have to choose between their own desires and what's best for the clan.
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.
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.