Well, 'oc' in fanfiction usually means 'original character'. In 'The Irregular at Magic High School' fanfics, original characters can add new storylines. They might be a new student with unique magic abilities, which could interact with the existing characters in interesting ways, like getting involved in the power struggles within the school or forming unexpected alliances.
Another interesting one is 'The Enchanted Highschool DxD'. In this fanfiction, the author delves deep into the magical lore of the Highschool DxD world. The magic is not just used for fighting but also for solving various mysteries within the school. It has a great blend of magic, mystery, and the typical Highschool DxD elements.
Another theme is mystery-solving. The 'oc' could be involved in uncovering secrets about the magic high school or the origin of certain magic abilities. It adds an element of suspense to the story, like the 'oc' finding out about a hidden magic society within the school.
One common theme is the power struggle. Students often have different levels of magical power, which leads to competition and sometimes envy among them.
One great Highschool DxD Issei magic fanfiction is 'Issei's Magic Evolution'. It shows Issei developing unique magical abilities that are different from his usual power set in the original series. This adds an interesting twist to his character.
The combination of high school drama and magic is also a big draw. In these fanfictions, characters use magic to deal with typical high school problems like bullies or academic challenges, but on a much more fantastical level. It's a unique blend that gives a fresh perspective on both high school and magic themes. Also, the fan - created characters in these stories often bring new dynamics to the relationships and power structures in the Highschool DxD world.
One of the main themes is the concept of being an 'irregular' in a highly structured magic society. It shows how the protagonist, Tatsuya, stands out and challenges the norms. Another theme is family and loyalty, as Tatsuya's relationship with his sister plays a significant role. Also, power and politics within the magic high school and the broader magic community are important themes.
Another reason is the fan community. Highschool DxD has a large and passionate fan base. When a fanfiction focuses on Issei and magic, it combines two elements that many fans are interested in. Fans like to share and discuss these fanfictions, which further spreads their popularity. Also, it allows fans to explore their own ideas and interpretations of the characters and the world, which is always appealing.
The magic system in Harry Potter could be integrated by having characters from Highschool DxD learn spells. For example, Issei could learn the Wingardium Leviosa spell to lift objects during battle, giving him an unexpected advantage. The Portkey concept could also be used to transport characters between the two worlds quickly.
A prevalent theme is also crossovers. Since it's a fanfiction combining Highschool DxD and Magic Knight, there are a lot of crossovers where the worlds and rules of the two series interact. For example, the magic systems of Magic Knight might be incorporated into the world of Highschool DxD, creating new and exciting storylines. And of course, the theme of adventure is also common as the characters embark on various quests and battles.