One interesting fanfic concept could be a time - travel scenario. Rias and Riser are sent back in time to when their families first had their feud. They then try to change things so that their present - day relationship is not so hostile. They face many challenges along the way, like trying not to change too much of the past and dealing with the different power dynamics of that era.
Perhaps a fanfic where Rias and Riser are both cursed by an ancient magic. They have to work together to break the curse. During this time, they discover secrets about each other's pasts that they never knew before. This could lead to a deeper understanding and a new - found friendship between them.
A great fanfic idea could be that Rias and Riser are sent on a joint mission to the human world. They have to blend in as high school students. This would be a comical and interesting premise as they struggle to adapt to human life while also dealing with their own relationship. Rias might be more empathetic towards humans, while Riser could be more arrogant at first.
One possible fanfic could be about a friendly rivalry between Rias and Riser that turns into a mutual respect. For example, they could start competing in various magical challenges within the Highschool DxD universe. This would show their growth as characters and how they overcome their initial differences.
One idea could be a story where Rias and Riser are forced to team up against a common enemy that threatens both of their peerages. This would put them in a situation where they have to set aside their differences and learn to work together. As they do so, they gradually start to understand each other better and a newfound respect develops between them.
One possible fanfic could be about Riser and Kuroka forming an unlikely alliance. Maybe they start off as enemies, but due to some common goal, like protecting the underworld from a new threat, they have to work together. Their interactions would be filled with tension at first, as Riser is quite prideful and Kuroka is independent. But as time goes on, they start to understand and respect each other more.
Their relationship could be developed uniquely by having them exchange roles. For instance, Rias could take on some of Riser's responsibilities in the Underworld for a while, and Riser could do the same in Rias' territory. This would give them a deeper understanding of each other's worlds and the pressures they face. They would then be able to support each other in new ways, leading to a stronger relationship.
In this fanfic, Riser and Kuroka might find themselves in a race against time. They could be competing with other factions in the Highschool DxD world to reach a certain place first. Maybe it's a place full of ancient magic that could give them an edge. Their different abilities would play a crucial role. Riser's fire - based powers and Kuroka's unique nekoshou skills would be used in creative ways to overcome obstacles.
One possible fanfic could be about their relationship as siblings in the context of the Highschool DxD universe. Maybe it could explore how Sirzechs' actions and decisions affect Rias. For example, his leadership in the Underworld might have an impact on Rias' development as a devil and her role in the school's Occult Research Club. It could also show how they support each other during difficult times, like when facing threats from other devil factions or powerful enemies.
One idea could be that Issei leaves Rias because he realizes he has different goals in the supernatural world. He might want to focus on helping the weaker devils rather than being part of Rias's peerage. So he sets out on his own journey, making new allies and facing new challenges.
There's a fanfic called 'Rias and Issei: A New Adventure'. In this one, they go on a journey together that tests their relationship. The author does a wonderful job of portraying their feelings for each other and the challenges they face as a couple in the world of Highschool DxD.
Power - up is a common theme. Fans often write about Riser getting stronger in unique ways, like mastering new magical abilities or combat techniques. It adds an exciting element to the stories.
Well, a fanfiction could focus on their daily lives outside of the battles. For example, Rias and Issei could have a cooking competition with their friends from the Occult Research Club. It would be a fun and light - hearted way to show their relationship and how they interact with the other characters in a non - combat setting.