A common theme is the fish - out - of - water situation. Naruto, coming from his own ninja world, has to adapt to the KHR world. This creates a lot of humorous and interesting situations. For example, he might use his chakra in ways that are strange to the KHR characters. Another theme is the building of relationships. Since it's a harem fic, Naruto forms different kinds of relationships with multiple female characters, from friendship to something more romantic.
Power - up is also a theme. Naruto often has to become stronger in the KHR world, either to protect himself or his new friends. His existing ninja powers might be enhanced or combined with the unique powers in the KHR universe. And of course, the harem theme itself is about the relationships. There's usually some jealousy or competition among the female characters for Naruto's attention, which adds drama to the story.
One common theme is power comparison. Since both series have their own magic systems, fanfics often explore how the powers in khr stack up against those in hp. For instance, the flames in khr vs the spells in hp.
One possible plot could be that Naruto somehow gets transported to the world of KHR. There, he meets the various characters and due to his unique abilities and kind heart, he attracts a group of them, forming a harem. They could go on adventures together, fighting against common enemies from both worlds while also dealing with the complex relationships within the harem.
One common theme is self - discovery. The OC often has to figure out their place in the Naruto world while being in a harem, which helps them grow as a character.
Another theme is the exploration of different cultures. Since Naruto and Bleach have their own unique cultures, the fanfic often delves into how these cultures interact when the characters are brought together. This can include things like how the ninja way from Naruto might be perceived by the Soul Reapers in Bleach, and how the hierarchies in both worlds are navigated in the context of the harem relationships.
One common theme is the clash of different personalities. Naruto has his own set of values and beliefs, and Serafall has hers. When combined in a harem setting, there are often clashes and reconciliations. Another theme is the development of relationships, not just romantic ones but also friendships within the harem.
Common themes in Naruto x small harem fanfics often include friendship and loyalty. Since Naruto has a big heart, he forms deep bonds with the members of his harem. Another theme is growth, not just for Naruto but also for the characters in his harem. They all grow together through various challenges and adventures.
In 'naruto x pregnant harem fanfic', a prevalent theme is likely to be the development of the harem itself. With the addition of pregnancy, it adds a new layer of complexity. There could be themes of jealousy and rivalry among the harem members, but also unity as they face the situation together. Additionally, the fanfic may touch on the cultural and social implications within the Naruto universe of having a harem and pregnancies within it, such as how the village elders or other characters react to this new situation.
The theme of growth is also prevalent. As they interact, both Bel and Fran grow as characters. They might become more empathetic or gain new skills. This growth is often a central part of the story, as it shows their development both individually and as a duo in the 'khr bel x fran fanfic'.
Love and friendship are common themes. Since they are characters from the same series, their relationship can be explored in terms of how a friendship can turn into something more. Also, growth is a theme. For example, Tsuna might grow more confident in his relationship with Haru, and Haru might grow more independent while still being close to Tsuna.
In this type of fanfic, Naruto is the central figure. From KHR, Gokudera would be a likely candidate for the harem. His loyalty and fiery personality would make for an exciting relationship with Naruto. Bianchi could also be part of it. Her cooking skills and her feelings for Gokudera could add an extra layer of drama. And Fon, with his calm and powerful presence, would be an important character interacting with Naruto in the harem - centered story.