Well, family bonds are a big theme. It shows how a father - son relationship between them would function. Also, inheritance is often explored. Not just of All Might's quirk, but also his legacy as a hero. And there's the theme of protection. All Might would be extremely protective of Izuku, and this is shown in different ways in various fanfics. Some fanfics also focus on how this new relationship would change the perception of Izuku among his peers and in the hero community.
One common theme is the revelation of their relationship. How Izuku discovers that All Might is his father and how he reacts to it. Another is the training aspect. Since All Might is a great hero, he can give Izuku more personalized and intensive training.
One common theme is the struggle with identity. Izuku would have to deal with the fact that his father is a major villain. Another theme is power. He might inherit some of All For One's powers in different ways, and how he uses or resists those powers. Also, redemption could be a theme. Maybe Izuku tries to atone for his father's actions in some fanfics.
Friendship and rivalry are also common themes. Just like in the original story, a female Izuku would have friends and rivals. Fanfics might explore how these relationships are different or similar. For example, her relationship with Bakugo could have a new dynamic. It might also show how she bonds with female characters in ways that a male Izuku might not.
Well, often you'll see themes related to the relationship dynamics. For example, how his relationship with his partner (whoever that may be in the fanfic) changes. There could also be themes about the future of Izuku's hero career in light of the pregnancy, like whether he'll take a break or find new ways to be a hero while being a parent.
Often, there's the theme of Izuku building a unique team. Just like in a game, he recruits classmates or other characters who have skills that complement his. This team then goes on to face various challenges together, both in the hero world and in virtual gaming - like scenarios. There's also the theme of Izuku unlocking hidden powers or abilities through his gamer knowledge, which is really exciting for readers.
One common theme is rivalry - turned - friendship. Their initial intense rivalry in the original story often forms the basis, and fanfics explore how it can transform into a deeper bond. For example, they might start to train together and realize they can learn a lot from each other.
One common theme could be the relationship development between Momo and Izuku. The pregnancy might act as a catalyst for them to grow closer and face new challenges together.
A sense of isolation can be a theme too. Having a unique dragon quirk might make Izuku feel different from others at first. He could be ostracized or misunderstood by some of his peers. But then as the story progresses, he finds ways to connect with others and use his quirk for the greater good, turning that initial isolation into a strength.
A common theme is growth. Both Izuku and Setsuna often grow as characters, learning from each other's strengths and weaknesses. For example, Izuku might teach Setsuna about perseverance, while Setsuna could show Izuku how to be more adaptable.
One common theme is the exploration of power dynamics. Since All for One has such a powerful and complex set of abilities, and Izuku is the inheritor of One for All, there's often a play on how their powers interact or oppose each other. Another theme could be redemption. In some fanfics, All for One might be on a path to redemption through his relationship with Izuku.
In these fanfics, the theme of transformation is often present. Female Izuku might transform into a dragon or have dragon - like features, which represents a change in her identity. This ties into the theme of acceptance. Katsuki has to accept this new Izuku, and Izuku has to accept her own new identity. Also, the theme of adventure is common. They often go on adventures together, facing challenges that test their relationship and their individual strengths.