The combination of different universes. Ben 10 has a wide array of alien forms and powers, while Highschool DxD has its own unique mythology and set of characters. When combined, it creates a whole new set of possibilities for stories.
The contrast in the characters. Ben 10 is a young hero with a sense of adventure, while the characters in Highschool DxD have their own complex personalities and power dynamics. Seeing how they interact, like Ben's straightforwardness clashing or meshing with the more nuanced social structures in Highschool DxD, is really engaging. For example, Ben might not understand the hierarchical nature of the devil society at first, leading to some interesting misunderstandings and story developments.
It's interesting because it allows for creative crossovers. Fanfic writers can come up with new plotlines that involve Ben 10 using his powers to help or hinder the events in Highschool DxD. Maybe he uses his XLR8 form to outrun a powerful enemy in the DxD world, or he uses the Omnitrix to transform into an alien that can counter a particular magical ability in Highschool DxD. This mixing of two very different fictional worlds makes for a lot of exciting and unpredictable storytelling.
Well, it really depends on what you're looking for in a fanfic. If you like action - packed stories, look for ones where Ben 10 has to fight against powerful foes in the Highschool DxD world. There could be battles against powerful devils or fallen angels. On the other hand, if you prefer more character - driven stories, there are fanfics that explore how Ben's experiences in his own world shape his interactions in the Highschool DxD world, and how his presence affects the relationships between the characters in the DxD series.
The combination of different universes. Highschool DxD has its own unique world of devils, angels, and other supernatural beings. Naruto has ninjas and a complex world of chakra. When you mix Rossweisse from Highschool DxD with the Naruto universe, it creates a lot of interesting possibilities for crossovers. Maybe Rossweisse could learn ninjutsu, or the Naruto characters could interact with the devils and angels from Highschool DxD.
A unique and well - developed OC. If the original character has an interesting backstory, personality, and goals within the world of Highschool DxD, it can make the fanfic engaging. For example, if the Gamer OC has a special power or ability that is different from the existing characters in the series.
One interesting crossover could be the characters from Highschool DxD using Ben's Omnitrix. Imagine Issei using the different alien forms to fight his battles in the DxD universe. It would add a whole new level of power and strategy.
The unique personalities of Gasper and Xen. Gasper is a rather complex character, and Xen brings something new to their dynamic. Their relationship has the potential for a lot of growth and interesting interactions.
Character development is key. Seeing the relationship between Koneko and the reader grow and change over time can be really engaging. For instance, if the fanfic shows how the reader helps Koneko overcome some of her personal issues or insecurities, it adds depth to the story.
The character crossovers are a big part. Imagine Ichigo from Bleach meeting Rias from High School DxD. Their different personalities and goals make for really engaging storylines. Also, the fanfic writers can explore how the characters from one universe would react to the situations and rules of the other universe. For example, how would a Bleach character deal with the peerage system in High School DxD? It opens up a whole new world of possibilities for storytelling that makes these crossovers so interesting.
The contrast between Issei's more earthly and often brash nature and Gabriel's celestial elegance. It creates a dynamic that can lead to really interesting character interactions in the fanfic.
Well - developed characters make it interesting. If the original character (OC) has a unique personality, backstory, and goals, and their relationship with Gabriel is complex and evolving, it can be really engaging. For example, if the OC is a half - demon who struggles with their identity and Gabriel helps them come to terms with it.
One idea could be that Ben Tennyson somehow ends up in the world of Highschool DxD. Maybe his Omnitrix gets a strange power-up that transports him there. He could use his alien forms to interact with the characters in DxD, like using Four Arms in a fight against some of the devils or fallen angels.