One great 'Boku no Hero Academia Izuku' fanfic could be one where Izuku discovers a new, hidden quirk within himself that's not related to One For All. This could lead to him having to train in a completely different way and form new relationships with his classmates as they all try to figure out this new aspect of his powers.
Bakugo is often paired with Izuku. Their complex relationship can add a lot of drama to the detective story. Bakugo might be reluctantly helping Izuku or even be a suspect in the case Izuku is investigating.
One common theme is empowerment. Since female Izuku is often in a male - dominated world of heroes, these fanfictions usually show her rising above the challenges and proving herself. For example, she might have to face discrimination from some of the male characters at first but then shows them what she's made of.
One idea could be that Izuku develops his own unique quirk without the initial setbacks. Maybe he discovers a latent power within himself through intense training and self - discovery. This would change the entire dynamic of his journey in the hero academia. He could be more confident from the start and not have to face the same kind of ridicule and self - doubt.
I've also read 'The Unlikely Duo'. This fanfic takes a different approach. It starts with Izuku and Momo being paired up for a project that has nothing to do with hero work. They initially clash because of their different personalities, but as they get to know each other better, they start to realize they have a lot in common and a relationship slowly blossoms.
Obviously, Izuku Midoriya is the central character. Then there are often characters like Ochaco Uraraka, who could be part of the harem as she has shown an interest in Izuku in the original series. Tsuyu Asui might also be included as she is a close friend and could potentially develop deeper feelings for Izuku in fanfiction.
Often, a common element is a distorted view of Izuku's power. Maybe his One For All power goes out of control in a terrifying way. Another element could be that the normally friendly characters in the Boku no Hero Academia world turn against Izuku, creating a very scary and isolating situation for him.
The character of Izuku is very relatable. He starts off as an underdog, which many readers can identify with. Fanfics allow writers to explore different scenarios where he overcomes his weaknesses in various creative ways.
A major theme is also the idea of support. The characters in the harem are often there to support Izuku in his journey to become a great hero. This can include emotional support, like when he's feeling down about his progress, or practical support during battles or training. And of course, there's the theme of love and attraction, which is a fundamental part of any harem story. Different characters in the harem will show their love for Izuku in various ways, whether it's through acts of kindness, protecting him, or just being there for him.