Imagine an OC who is a half - devil, half - dragon. They are shunned by both the devil and dragon communities. The OC's goal could be to find a place where they belong. In the process, they discover a conspiracy that threatens the balance between the different supernatural races. They then have to use their unique abilities, which combine devil magic and dragon strength, to save the day. This would create a story with themes of acceptance and self - discovery.
One plot idea could be an OC who is a reincarnated angel in the Highschool DxD world. The OC has to hide their true identity while trying to stop a secret group of devils from starting a war between the three factions. They could team up with Issei and his friends, but there would be constant suspicion from the devils around them.
One idea could be an OC with a unique sacred gear that has powers no one has seen before. For example, a sacred gear that can manipulate time on a small scale, allowing the OC to freeze time briefly during battles in Highschool Dxd's universe. This would add a whole new dynamic to the battles and interactions.
Well, you could make an OC that is a half - angel, half - devil. This would give the character a very complex backstory and internal conflict, especially in the world of Highschool DxD where the angels and devils have their own politics and power struggles. Also, for the OP part, this OC could have a special ability to combine angelic and demonic powers in a new and powerful way.
There's a fanfiction where the op oc gamer has the power to level up like in a game. In this story, they use their unique skills to navigate the complex world of Highschool DxD, making allies and facing off against powerful foes. It's really exciting as it combines the game - like mechanics with the supernatural elements of the series.
One plot idea could be that the male OC discovers he has a rare and powerful sacred gear that everyone wants to get their hands on. This leads to him being hunted by different factions. Another idea is that he accidentally enters a secret realm within the DxD world that has been lost for centuries and has to find his way out while uncovering its secrets.
One idea could be Shirou using his projection magecraft in the Highschool DxD world to create unique weapons during battles against the devils or fallen angels. For example, he might project Excalibur to fend off a powerful devil attack. Another plot could involve Shirou forming an alliance with Issei and his group, teaching them about his different combat techniques and how to better strategize in fights. He could also have a romantic sub - plot with one of the female characters from Highschool DxD, like Rias, where his noble and self - sacrificing nature attracts her.
A plot could revolve around the Sharingan OC being a target because their Sharingan is seen as a powerful tool. Devils might want to use it for their own gain, and angels might see it as a threat. The OC then has to fight to protect themselves and their friends. Also, the OC could use their Sharingan to unlock a hidden power within Issei, which changes the power balance in the DxD world. Another idea is that the OC comes from a parallel world where the Sharingan and DxD powers are combined, and they are on a mission to bring balance to the DxD world.
One popular 'Highschool DxD' OP OC fanfiction is 'The Red Dragon Emperor's New Path'. It offers a unique take on the story with an original character who has overpowered abilities and embarks on a different journey within the 'Highschool DxD' universe. The character development in this fanfiction is quite engaging as the OC has to deal with the complex politics and power struggles in the world of devils, angels, and fallen angels.
A plot could involve the mute OC being a new transfer student in the school. Their muteness makes them an object of curiosity and some characters might initially misjudge them.
One idea could be that the OC is a new transfer student to the school and immediately catches Kuroka's attention. They start off as rivals in magic or combat skills, constantly trying to outdo each other. As time passes, they realize they have more in common than they thought and gradually fall in love.
A good plot for Highschool DxD fallen angel OC fanfiction could start with the OC being hunted by a group of vengeful angels. As they run, they end up in the territory of the devils and have to make a deal with them to survive. Along the way, they fall in love with a devil, which creates a whole new set of problems as their two worlds collide. Or, the OC could be trying to solve a mystery that dates back to the very beginning of their fall, something that involves a prophecy that only they can fulfill.