Highschool DxD OC x Rias Harem Fanfiction: What are some interesting plot ideas?

One idea could be the OC having a unique power that attracts the various characters in the harem. For example, if the OC can manipulate time in a certain way, it could lead to some really interesting situations. Maybe they use this power to save a member of the harem from a dangerous situation, which then makes that character develop strong feelings for the OC. Another plot idea is the OC being from a different dimension and having to adapt to the Highschool DxD world while building relationships with the harem members.

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.

The OC could be a new transfer student with a mysterious past. As the story progresses, it's revealed that they are on a quest to find a powerful artifact that is somehow connected to the characters in the harem. This could lead to adventures together, and the building of deeper relationships within the harem.

One idea could be an OC who is a transfer student with a unique power. The harem could form as different characters in the Highschool DxD world are intrigued by this power and gradually fall for the OC. For example, the OC might have the ability to heal wounds instantly, which is very useful in the battles that often occur in the DxD world.

One idea could be an OC who is a transfer student with a unique power, like the ability to manipulate time slightly. This catches the attention of the main characters in the Highschool DxD world. The harem could start to form as different characters are intrigued by the OC's power and mysterious background.

One idea could be an OC who is a transfer student with a unique power that no one in the Highschool DxD universe has seen before. This power could attract the attention of the main characters and lead to various adventures and alliances.

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 the OC is a skilled musician and Sona, who has an appreciation for the arts, meets the OC at a school concert. They start collaborating on music projects and their relationship blossoms from there. The OC could also have some sort of hidden past related to the supernatural world that Sona helps them uncover.

Maybe the OC is an artist who can create magical art. Akeno is fascinated by this art and the emotions it evokes. They could start collaborating on projects that are not only artistic but also have a deeper meaning in the context of the Highschool DxD universe. For instance, creating art that can temporarily shield them from attacks or art that can influence the minds of their enemies. Their relationship could grow as they explore the potential of the OC's art together.

Maybe the OC Sitri is from a different branch of the Sitri family that has been in hiding. Their appearance in the story could stir up old rivalries or create new alliances. They could bring with them ancient knowledge or artifacts that change the power dynamics in the Highschool DxD world.