The OC's personality can be a major factor in standing out. If the OC has a very strong sense of justice and is not afraid to speak up against wrongdoings, even in a world full of powerful demons and angels. This kind of moral courage can attract the attention of characters like Issei, who himself is on a journey to become a better person. The OC's unique personality traits would make them different from the other characters in the series and thus be able to form a harem.
An OC could stand out by having a special skill or talent. Maybe the OC is an amazing cook and can make the most delicious food. In a world where battles and magic are common, this simple yet appealing talent could draw in characters from the series. They would be intrigued by this different side of the OC and gradually form a harem around them. It also gives a chance for some cute and comical interactions, like when the characters are all eagerly waiting for the OC's next meal.
The OC can stand out by having a distinct personality. For example, if all the other harem members are bold and outgoing, the OC could be more reserved and intellectual. This contrast would make them interesting. Also, a unique skill or ability, like being able to communicate with spirits, would set them apart.
The OC can stand out by having a distinct personality. For example, if most of the harem members are more on the outgoing and aggressive side, the OC could be calm and collected. Their different approach to situations would make them noticeable. Also, having a unique power or ability that no one else in the harem has would definitely set them apart.
The OC could have a unique appearance, like having heterochromatic eyes, one gold like Lucifer's and one a deep purple. Their hair could be a color not seen often in the series, such as silver. And they could have a special mark on their body that is related to their power or connection to Lucifer.
Giving the elf OC a distinct personality trait. Such as being extremely curious about human technology and constantly trying to incorporate it into their elven magic. This would create humorous and interesting situations as they interact with the other characters who are more used to traditional magic and may not understand their fascination with modern gadgets.
A Highschool DxD SI Gamer OC fanfiction can stand out by having a really unique SI OC design. For example, if the character has a very distinct backstory related to their gaming experience, like they were a pro - gamer in a previous life and now they have to use those skills in the Highschool DxD world. This makes the character more interesting and different from the regular characters in the series.
Incorporate unexpected plot twists. Instead of the usual battles between the factions, have your OC accidentally start a new conflict that no one saw coming, like a conflict over a new type of power source that has emerged in the Highschool DxD world. This will keep readers engaged.
First, give your OC a distinct personality. Don't make them a typical 'good guy' or 'bad guy'. Maybe they have a sense of humor that's a bit dark or they're overly polite in a world full of brash characters. Second, their power should have a unique origin. It could be something like they got their power from an ancient artifact that was lost in the 'Highschool DxD' world.
First, focus on creating a unique backstory for your OC. For example, if your OC has a tragic past that led them to be who they are in the Highschool DxD world, it can make them more interesting. Second, give your OC distinct abilities or powers that are not commonly seen in the series. Also, develop their personality in a way that makes them different from the existing characters. They could be extremely introverted or have an unusual sense of humor.
Give your OC a distinct personality. For instance, if most characters are bold and brash, make your OC more reserved and calculating. This contrast will make them stand out.
Unique character design. If the original character (OC) has a distinct personality and backstory that fits well within the Highschool DxD universe, it can make the fanfiction stand out. For example, an OC gamer who has a special power related to gaming that also has an impact on the DxD world in an unexpected way.