A plot could revolve around the mystery of the baby's powers. Since Rias is a powerful devil, there could be speculations about what kind of abilities the baby will inherit. This could lead to various groups either trying to protect Rias and the unborn child or trying to use the baby for their own purposes. Rias would then have to fight to keep her baby safe while also preparing for motherhood. The story could also show how her friends and allies in the Highschool DxD world support her during this time.
Well, a possible plot could be Rias having to balance her pregnancy with her studies at school. She's not just a devil but also a student. There could be comical moments like when she has sudden cravings during class or struggles to fit into her school uniform as her body changes. Also, the relationship between Rias and Issei could deepen in new ways. They might have to face challenges together, like dealing with over - protective family members from both the human and devil sides.
One idea could be a story where Issei and Rias have to face a new, powerful enemy that targets their relationship. Maybe an ancient demon who sees their bond as a threat to the traditional demon hierarchy. Another plot could be a time - travel story where they go back in time and have to deal with past events that could change their present relationship. For example, they might have to stop an event that would have otherwise led to their separation.
One idea could be that the OC has a unique power that helps Rias and her harem in unexpected ways. For example, the OC might be able to sense danger before it arrives, allowing them to better prepare for battles against other factions. Another plot could involve the OC having a past connection to one of the members of Rias' harem, which creates some drama and tension as they navigate their new relationships within the harem. Maybe the OC is a long - lost relative or an old friend who has changed a great deal.
A fanfiction could explore their past. For example, how they first met in the underworld. It could show their initial impressions of each other and how their relationship developed over time. Perhaps there was some sort of competition between them at first, but they later realized they could be great friends and allies. This would give readers a deeper look into their characters.
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.
Perhaps a plot where a pregnancy occurs as a result of some sort of magical or supernatural accident in the Highschool DxD world. The story could then focus on the search for a way to reverse it or deal with it. Along the way, the characters might discover new powers or secrets about their world. And the relationships between the characters could be tested as they face this difficult situation together.
One idea could be that the male OC has a unique power that Rias needs to protect her peerage. So they start working closely together, and slowly feelings develop. For example, the OC might be able to sense impending danger to the group in a way no one else can.
Well, in some fanfictions that depict Rias as a spoiled brat, they might show her using her status and power to get what she wants in the Highschool DxD universe. For example, she could be overly demanding with her peerage members.
One idea could be a story where Issei and Rias have to go on a special mission together in a parallel dimension. In this dimension, they lose their powers and have to rely on their wits and the bond they've developed. They face challenges that test their relationship and force them to understand each other on a deeper level.
A great Rias fanfiction could focus on her relationships outside of the main group. Maybe she befriends a human who has no knowledge of the supernatural world. It would be interesting to see how she tries to protect this new friend while also hiding her true identity as a devil.
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.