One common theme is redemption. Since they have a new chance at life through reincarnation, often Sasuke gets a chance to atone for his past mistakes. For example, in some fanfics, he uses his new life to make up for the pain he caused in his previous life.
Power exploration is also common. Reincarnated characters often have unique powers or knowledge from their past lives. They use these to become stronger or to figure out the secrets of the Naruto universe, like unlocking hidden jutsu or understanding the origin of certain clans.
One common theme is redemption. Sasuke has done a lot of things that some might consider wrong, and in many fanfictions, Naruto is the key to his redemption. Another theme is friendship. Their bond is often explored in different ways, like how they support each other in tough times. Also, the idea of power and how they use it together or against each other can be a theme.
Another theme is redemption. Sasuke's actions in the original story make his path to redemption a popular topic. Fanfictions might show how Naruto helps him find his way back to the good side. For example, in some stories, Sasuke has to make amends for his past deeds with Naruto's support.
The theme of growth is very common. All three characters - Naruto (the adopter), Naruto (the younger self) and Sasuke - experience personal growth. They learn from each other, share their skills and knowledge. For example, Naruto might teach Sasuke some new jutsu, while the younger Naruto learns about the importance of friendship from Sasuke. This mutual growth is what makes these fanfictions interesting.
The theme of sacrifice also shows up a lot. Both Naruto and Sasuke are characters who are willing to sacrifice for the other in the original story, and this is often explored further in fanfiction. Writers might create scenarios where one has to make a big sacrifice for the other, which then tests and deepens their relationship.
Another theme is the interaction between Urahara and the existing Naruto characters. He might form alliances or rivalries. For instance, he could team up with Naruto to fight against a common enemy, or he might have a rivalry with Sasuke due to their different views on power. Also, the exploration of how Urahara's Bleach - related powers could be translated into the Naruto universe is quite common. His scientific knowledge in Bleach could be turned into something related to ninjutsu research in the Naruto world.
One common theme is the use of gaming knowledge. For example, the protagonist might know about strategies from games and apply them in battles in the Naruto world. Another theme is power - leveling. They often start from a weak state and use their gamer - like approach to gain strength quickly.
Well, in 'Naruto Reincarnation of Ulquiorra' fanfiction, a very common theme is adaptation. Naruto has to adapt to having Ulquiorra's memories and powers. This can lead to some really interesting storylines, like him trying to use Ulquiorra's combat techniques in the ninja world. Another theme is the exploration of different cultures. Since Ulquiorra is from a different fictional universe, there could be a comparison or combination of the Bleach and Naruto universes' cultures. Additionally, the theme of friendship is often explored. Naruto's friends may have a hard time understanding this new Naruto, and the fanfiction could show how they try to maintain their friendship through these changes.
Power and its limits is another one. In these fanfictions, we see them constantly testing their powers. Naruto might be trying to master new jutsus without losing himself. Sasuke could be grappling with the power of his Sharingan and how far he should go with it. Kakashi, with his Sharingan and his own unique skills, also serves as an example of someone who has learned to control and use his power effectively within certain limits.
Another theme is the way she is perceived in the ninja world. As a girl, she may face different expectations and prejudices. Some fanfictions explore how she overcomes these and still manages to be a strong ninja. In many of these stories, she has to prove herself more because of her gender.