It could completely change the power dynamic in the story. Naruto with the Rinnegan would likely become almost invincible, making his battles much less challenging.
It could be that he was in a life - or - death battle against a powerful enemy. Maybe he was pushed to his limits, and in that moment of extreme stress and desperation, his latent power awakened in the form of the Rinnegan.
Well, in a good Naruto Rinnegan fanfiction, the character development is key. Naruto should change in a believable way as he gains the Rinnegan. His relationships with other characters, like Sasuke and Sakura, should also be affected realistically. Additionally, the plot should be engaging. It could involve Naruto using the Rinnegan to face new and powerful enemies, or to solve long - standing problems in the ninja world. For instance, he might use it to finally end the cycle of hatred. The story should also stay true to the overall Naruto universe in terms of its rules and the nature of the characters.
In some fanfictions, it could be through a strange and powerful jutsu transfer. Maybe Madara, on the verge of defeat, decides to transfer his Rinnegan power to Naruto for some unforeseen reason, like seeing a new path for the ninja world in Naruto.
Well, there's a fanfic called 'Naruto's Rinnegan Adventure'. In this story, Naruto discovers the Rinnegan early on and has to deal with the consequences. It's interesting as it shows how his relationships with his friends and the village change due to this new power. Also, 'Rinnegan - Naruto's New Path' is a good one. It follows Naruto as he uses the Rinnegan to reshape the ninja world, facing many challenges along the way.
Power. Most fanfictions focus on the extreme power of Madara's Rinnegan. They explore how it can be used to dominate battles or change the Naruto world. Another common theme is mystery. Since the Rinnegan has many unexplored aspects in the original series, fanfictions often try to uncover its secrets.
One possible reason could be a search for power. The character might feel that Konoha doesn't offer enough resources or training opportunities for them to fully explore the potential of the Rinnegan. They may believe that there are other places in the Naruto world where they can gain more knowledge and power related to their special eye.