Some asta harem fanfic may focus on the cultural or social aspects within the fictional world where the harem exists. It could explore how the concept of a harem is perceived in that world. Additionally, there might be themes related to adventure. Maybe Asta and his harem go on quests together, and during these adventures, their relationships deepen. This can include facing enemies together and relying on each other, which in turn strengthens their bonds.
Noelle Silva is often included. She has a pre - existing relationship with Asta in the original story, and in fanfic, it's easy to expand on that into a more romantic connection. Another one is Mimosa Vermillion. Her kind nature makes her a likely candidate for the harem. Also, Nero is sometimes part of it as she has her own unique connection to Asta.
Since lemon fanfics are inappropriate, we should focus on their general characteristics from the official story. Asta is highly determined and energetic, always striving hard despite his lack of magic initially. Yuno, on the other hand, is more calm and has a natural talent for magic. They both have a strong bond as rivals and friends.
Noelle could be a great addition. Her water magic is quite powerful and she has a complex relationship with both Asta and Yuno. She could be a source of both support and conflict in the fanfic. Another good character is Luck. His lightning magic and his rather unpredictable nature can add a lot of action and excitement to the story.
Asta would likely bring a new level of determination to the Crimson Lions. His never - give - up attitude could inspire the team members during tough battles.
Asta could be brought into the High School DxD fanfic as a result of a multiverse - related event. In this case, different universes are colliding or being connected in some way. His presence would disrupt the power balance as his anti - magic is something that no one in the High School DxD world has really encountered before. He could end up training with the devils to learn more about their magic while also teaching them about the concept of anti - magic.