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.
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.
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.
First, you need to know the characters well. For Ben 10, understand his different alien forms and their powers, as well as his personality. In Highschool DxD, know the abilities and relationships of characters like Issei, Rias, etc. Then, create a unique plot. It could be something like a tournament where Ben's aliens compete against the supernatural beings of DxD.
The plot could involve Ben's aliens having an unexpected effect on the magic in the Highschool DxD world. His alien DNA might interact with the devil or angel powers in strange ways. For instance, if he transformed into Heatblast near a magic spell, it could cause the spell to go haywire. And his presence could also disrupt the power balance between the different factions in the DxD world, leading to new alliances and rivalries.
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.
There is also 'Koneko's New Path'. This fanfic delves into a different scenario where Koneko has to face unique challenges that are not in the original plot. It's interesting as it gives a fresh perspective on her character. For example, she has to make difficult decisions about her loyalty to different factions, which really showcases her complex personality.
A 'ben dxd fanfic' is likely a fan - made fictional work related to the series 'High School DxD'. It could involve creating new storylines, character developments, or alternate universes within the context of that show. It might focus on different relationships between the characters, new adventures they embark on, or unique interpretations of the existing plot elements.
Naruto would probably be very friendly and curious. He'd be excited to meet all the different types of beings in the Highschool DxD world. He might start by trying to make friends with Issei, sharing his stories about his own battles and adventures in his world.
Perhaps a fanfic where Risa is a new transfer student and Sirzech is assigned to show her around. Along the way, they get involved in a mystery involving missing students. Their relationship could grow as they work to solve this mystery, with Sirzech protecting Risa at times and Risa using her wits to help Sirzech in making crucial decisions.