A recurring theme is the discovery of new things. Harry discovers new aspects of Rias' world and vice versa. It's like exploring uncharted territory. Also, there's often a theme of loyalty. As they face difficulties, they show loyalty to each other which is an important aspect of their relationship in these fanfictions. These themes together create a rich and interesting reading experience.
One common theme could be the clash of different cultures. Harry comes from the wizarding world in England with its own set of rules and traditions, while Rias is from a different kind of supernatural world. Another theme might be the power dynamics. Both characters have their own forms of power, and exploring how they interact with each other in terms of power and support in their relationship could be interesting. Also, there could be a theme of discovery, as they learn about each other's worlds and abilities.
A common theme is the clash of different cultures. Harry comes from the wizarding world with its own set of rules and traditions, while Rias is from a world of devils. Another theme is power exploration. Harry has his magic, and Rias has her devil powers, and in fanfictions, they often explore and combine their powers in new ways.
Since I don't really promote or encourage 'lemon' fanfiction which often has adult - themed content, I can't accurately say what the common themes are in that specific type. But in general Harry and Rias crossovers might have themes like power dynamics, as Harry has his own set of magical abilities from the Harry Potter world and Rias has her devil powers in High School DxD. Another could be cultural clash, as they come from very different fictional settings.
Well, the theme of sacrifice is quite prevalent. Sometimes either Issei or Rias has to sacrifice something for the other or for the greater good. Another common theme is identity. Issei, as a human - turned - supernatural being, and Rias, as a devil, both struggle with their identities at times. Their relationship helps them to better understand themselves. And the theme of destiny often comes up, as if they are fated to be together and face all these challenges as a couple.
One common theme is the exploration of relationships. For example, romantic relationships between characters that were not fully explored in the original books, like the relationship between Harry and Hermione. Another theme is the expansion of the magical world, such as new spells or magical creatures. Also, there are fanfictions that focus on the backstories of minor characters, giving them more depth and significance.
Love and sacrifice are also prevalent themes. We see how the love of Lily Potter saved Harry in the original series, and fanfiction often expands on this idea of love being a powerful force. There are also fanfictions that explore the idea of redemption for characters like Draco Malfoy, showing that even those on the wrong side can have a chance at changing and making amends.
One common theme is adventure. Combining the action - packed world of 007 with the magical adventures of Harry Potter makes for some thrilling stories.
In such a fanfiction, Harry Potter might grow up with a very different set of values. Rias is from a different fictional universe with her own code of conduct. He could be trained in devil - related magic or combat skills that are unique to her world. Maybe he would be more assertive in relationships as Rias is quite bold in that aspect.
The plot could involve Harry learning about his connection to Rias. He could be sent on a quest that is related to both his Potter identity and his relation to Rias. For example, he might have to find a magical artifact that is important to both his father's side (the Potter side) and Rias' side. Along the way, he would make new friends and enemies, and his skills as a wizard would be put to the test in different ways than in the original Harry Potter series.
A 'Harry Potter marries Rias' fanfiction could involve a lot of cultural clashes at first. Harry is used to the British wizarding society's rules and norms, while Rias has her own set of values from her world. However, their shared love for magic (in different forms) could be the basis for their relationship. They might have to face many challenges together, like dealing with the pure - blood supremacists in Harry's world who might not accept his union with someone from a completely different magical realm, and also Rias' own allies and enemies in her world who may not understand her choice.