Often, Naruto might be paired with Madara in some sense. Their opposing views on power and peace could create interesting interactions in the fanfiction.
Well, in such a fanfiction, Madara's training might enhance Naruto's physical strength. He could teach Naruto some advanced Uchiha techniques which Naruto can combine with his own Uzumaki powers. For example, Naruto might learn better chakra control from Madara, enabling him to use his Rasengan more effectively and with less chakra waste.
First, you need to understand Madara's character thoroughly. Know his motives, his powers, and his place in the Naruto universe. Then, create an OC that can interact meaningfully with him. For example, if your OC is a pacifist, how would they deal with Madara's more violent tendencies? Make sure to have a solid plot that ties in with the Naruto lore.
In fanfiction, Naruto and Madara Uchiha's sister could be connected in various ways. For example, she might be a secret ally who helps Naruto understand the Uchiha clan better. Maybe she has some long - lost knowledge about the Sharingan that she imparts to Naruto to help him in his battles.
Madara would have to adapt to the different threats in RWBY, mainly the Grimm. In his world, he was used to fighting other shinobi and clans. The Grimm are a whole new type of enemy. However, his Sharingan would give him an advantage in detecting their movements. He might also try to find a way to use the Grimm's negative energy, similar to how he used negative emotions in his own world to fuel his power.
No. Naruto has his own unique story and character development that is distinct from simply being a fanfiction of Uchiha Madara. Naruto is about his journey to become Hokage, his relationships with his friends like Sasuke, Sakura, etc. His goal is to bring peace to the ninja world in his own way, through understanding and friendship. While Madara is an important part of the Naruto lore, Naruto's story is not centered around being a fanfiction of Madara. He is his own hero with his own dreams and challenges that are not directly related to being a fan of Madara.
Yes, there might be. The world of fanfiction is vast and full of crossovers. Fans often like to combine different fictional universes, so it's very possible that someone has created a story where Harry Potter is a fan of Madara Uchiha. You can search on various fanfiction platforms to find out.
In fanfiction, the author could create a scenario where there was a secret relationship between an Uzumaki ancestor of Naruto and an Uchiha. This relationship could have been hidden for generations. And through some family secrets being revealed, it's discovered that Naruto is actually Madara's grandson. It could also involve some kind of genetic manipulation or curse that ties the two families together in a way that wasn't known before.
One possible way is through some sort of powerful jutsu gone wrong. Maybe a forbidden jutsu that was meant to do one thing but instead warped Naruto's being and made him take on the form and some of the characteristics of Madara Uchiha. It could also be the result of some dark magic or curse that was placed on him by an enemy who wanted to disrupt the balance in the ninja world.
To make the OC believable, give them relationships. They could have friends or enemies outside of Madara. These relationships will shape their character. For example, if they have a best friend who was killed by a rival clan, it could fuel their desire to get stronger. Also, let their character develop over time. Don't make them perfect from the start. They should learn from their experiences, especially those involving Madara. Maybe at first they idolize him, but as they see his darker side, they start to question his methods.