Well, a common theme is the alteration of relationships. With the Evil Rinnegan, Naruto's relationships with his friends and allies could change drastically. For example, some friends might be scared of him or turn against him. And in terms of the story's setting, it often involves a darker, more dangerous world. Since Naruto has this evil power, the balance of power in the Naruto universe is disrupted. Enemies might be more aggressive or new, more powerful enemies could emerge, drawn to the power of the Evil Rinnegan. It also often has themes of mystery, as the origin and true capabilities of the Evil Rinnegan in these fanfictions are usually something to be uncovered.
The theme of isolation is often present. Naruto, having the Evil Rinnegan, might find himself isolated from those he once cared about. His new power could be seen as too dangerous or his actions too extreme. Another theme is the exploration of different jutsu combinations. The Evil Rinnegan might give Naruto access to new and terrifying jutsu, and fanfictions might explore how he uses these in battles. And sometimes, there's a theme of a hidden agenda. Maybe there's a greater force behind Naruto getting the Evil Rinnegan, and the story unfolds as he discovers this hidden agenda and decides whether to go along with it or fight against it.
One common theme is power exploration. Writers often delve into how Madara's Rinnegan powers could be used in different scenarios, like battles against other powerful foes. Another theme is redemption. Some fanfictions might explore if Madara could be redeemed with his newfound power. And of course, there are also stories about his past and how he obtained the Rinnegan in the first place.
Well, a frequent theme is probably the struggle for identity. In these kinds of fanfictions, a character with the Rinnegan might be grappling with who they are now that they have this powerful dojutsu. Are they still the same person? Do they become something else entirely? Also, the theme of redemption could be present. Maybe the character has done some bad things because of the Rinnegan's power, and they are trying to make up for it. It's like they are on a journey to find themselves and regain their moral compass.
The Akatsuki as a whole could be antagonists. In fanfictions, the Akatsuki might be interested in the power of Naruto's Evil Rinnegan. They could try to capture him to extract the power or use him in some way for their own goals. Pain, being a powerful member of the Akatsuki, could also be a specific antagonist. His own ideology about pain and peace might clash with Naruto's new, potentially more chaotic state with the Evil Rinnegan. Additionally, new original antagonists created specifically for the fanfiction could be common. These could be dark, powerful figures who are drawn to the power of the Evil Rinnegan and want to either possess it or destroy Naruto to prevent its misuse.
One common theme is power and its consequences. When a female Naruto has the Rinnegan, she has to deal with the great power it brings. For example, she might face envy from other ninjas or the temptation to use it for wrong reasons.
A frequent theme is adaptation. When the Rinnegan is introduced into a crossover, characters have to adapt to this new power dynamic. For example, in a Naruto - Harry Potter crossover, the wizarding world has to adapt to the existence of the Rinnegan. Also, redemption can be a theme. A character who has misused the Rinnegan may seek redemption in the crossover story.
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 interesting concept could be how Naruto's character changes with the Rinnegan in an evil context. Maybe his views on power and friendship shift drastically. For example, he might use the powers of the Rinnegan to control others instead of protect them.
One common theme is adaptation. The self - inserted character has to adapt to the world of Naruto with the Rinnegan. They need to learn how to fit in with the existing ninja culture while also dealing with the new - found power. Also, redemption can be a theme. Maybe the character made mistakes in their past and now with the Rinnegan, they try to make up for it by using its powers for good in the Naruto world.
Another common theme is the relationship between Naruto and the fem Kyuubi. It could be a partnership, a friendship, or something more complex. The story often explores how they interact and grow together with this new situation of the fem Kyuubi having the Rinnegan.
Crossover chaos is also a theme. These fanfictions bring two very different universes together. So, there's often a sense of chaos as the rules, cultures, and characters from Naruto and Soul Eater collide. For example, in 'The Blended Realms', the different fighting styles and values from both series create a lot of interesting and sometimes comical situations.