One idea could be Kiba getting involved in a secret magical tournament within the school. Another could be him forming a special alliance with an unexpected character to solve a mystery. Maybe he discovers a new power that changes his role in the school's supernatural hierarchy.
One plot idea could be that Kiba and Naruto are paired up for a school project. They start off bickering but gradually realize they have a lot in common and form a strong friendship that might turn into something more. For example, they discover their shared love for adventure while exploring an old abandoned part of the school for their project.
Another plot could involve a time - travel scenario. Maybe a character accidentally sends themselves and some of their friends back in time to when the first devils were created. They would have to navigate this ancient world while also trying not to change history too much, or else it could have dire consequences for their present.
One idea could be a comical situation where a character accidentally releases a fart during a tense battle in the High School DxD world, and it somehow disrupts the enemy's attack. For example, the smell could be so bad that it makes the opponents gag and lose their concentration.
One idea could be Leviathan using her unique powers in a new way to solve a mystery within the school. For example, she might use her water - based abilities to uncover hidden passages or secrets. Another could be a story where she forms an unexpected alliance with a character from a different faction to face a common threat.
A possible plot is that the OC is a misfit who doesn't fit into the typical categories in the High School DxD world. They might be a human with no obvious supernatural powers at first, but through their wits and determination, they manage to form alliances with different factions. They could use their knowledge of human technology and psychology to gain an edge, and along the way, they develop a unique power or ability that no one expected.
One idea could be a yandere character who is secretly in love with Issei but her yandere tendencies start to cause chaos in the Occult Research Club. She might try to eliminate any girl who gets too close to him, leading to a lot of drama and action within the club.
One interesting plot idea could be that Kiba and Tsubaki have to team up for a special mission in the Underworld. They face various challenges and in the process, they discover new things about each other's pasts and their own powers. This could lead to a deeper bond between them.
A great idea for a High School DxD fanfiction is to explore a romantic relationship that is not the typical one in the series. For instance, a story about a relationship between two side characters who have to overcome many obstacles due to their different species or social status within the devil - angel - fallen angel hierarchy. You could also write about a character's journey of self - discovery outside of the main plot of the series. Like a character who realizes they have a different purpose in life than what they were initially led to believe.
One possible plot could be that Kiba is made out to be a bully in the High School DxD setting. He could be picking on characters from the DxD world, which angers the main characters from that series. This then leads to a conflict where the DxD characters team up with some Naruto characters who also don't like Kiba's behavior.
A possible plot in High School DxD Torture Magic Fanfiction is that there is a magical artifact that is powered by torture magic. Different factions in the High School DxD world are vying for this artifact. The story could follow the main characters as they try to either obtain the artifact for good reasons or prevent it from falling into the wrong hands. Along the way, they face many challenges related to the torture magic associated with the artifact, like having to resist its corrupting influence.