One great Issei fanfiction is 'Raising Hell with Issei'. It shows a different side of Issei's growth and his adventures in the Highschool DxD universe. The story has some really interesting plot twists that keep you hooked.
Ichigo could be a game - changer. His Hollow - like powers might be mistaken for some sort of demonic or otherworldly ability in the Highschool DxD setting. This could lead to both misunderstandings and interesting interactions with the characters there.
One possibility could be that Ichigo's powers would make him a very unique and powerful character in the Highschool DxD universe. His zanpakuto abilities and high - level combat skills could give him an edge in the battles against the devils and other supernatural beings in that world.
One common theme is power escalation. Since Issei is OP in these fanfictions, the story often focuses on how he continues to gain and control his ever - increasing power. Another theme is harem - related, as in the original Highschool DxD, Issei has a harem. In the fanfictions, his OP status might attract even more characters to his harem, and the dynamics within the harem change because of his new power level.
To create a compelling OC in Highschool DxD fanfiction, first think about their backstory. A tragic or mysterious past can add depth. For example, if your OC is an exiled devil, it gives a reason for their actions. Also, consider their powers. Make them unique but not overpowered to the point of being unbelievable. Maybe they have a special ability related to an element like shadow manipulation that ties into the DxD universe's lore.
Issei is a character that many fans can relate to in some ways. He starts off as an underdog and then grows in power. In fanfiction, this growth can be taken in all kinds of directions. Some fanfictions might explore his darker side, or his more heroic side. And since the Highschool DxD series has a large fan base, there are always people interested in reading new takes on Issei's story.
Interaction with the existing cast. A good fanfiction will have the OC interacting meaningfully with characters like Issei, Rias, and others. This can include forming alliances, rivalries, or even romantic relationships. It adds depth to the story and shows how the OC fits into the already established world of 'Highschool DxD'. Well - written fight scenes are also important. Since the OC is overpowered, the battles should be exciting and show off their abilities in a cool way, like using their powers in creative combinations against strong opponents.
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.
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.