One possible plot could be that Villain Deku is on a mission to undermine the hero society and crosses paths with Hero Deku. They engage in a fierce battle where Villain Deku taunts Hero Deku about his ideals. In the end, Hero Deku manages to get through to a small part of Villain Deku's conscience, leaving him with some doubts about his villainous path.
One common theme is empowerment. Female Deku often overcomes challenges in a different way than male Deku, showing her strength and determination. Another theme is relationships, like her friendships with other characters or potential romantic interests.
Villain Deku might start to question his villainous ways. Meeting Hero Deku could make him see the good in heroism. Hero Deku, on the other hand, could become more empathetic towards those who turn to villainy. He might realize that there are reasons behind it and not all villains are just 'evil' for the sake of it.
One popular 'My Hero Academia Female Deku' fanfic could be 'Deku's New Path'. In this fanfic, Female Deku might face different challenges than the male version. Another example could be 'Female Deku's Ascent' which might focus on her unique journey in the hero academy. There are also fanfics like 'The World Through Female Deku's Eyes' that can offer a fresh perspective on the My Hero Academia universe.
In fanfiction, a quirkless Deku often has to rely more on his wits. Canon Deku got One For All, but in fanfic, he has to find other ways to be strong. For example, he might study different fighting styles more intensively.
Toga could be an ally. Since she has her own complex relationship with the idea of heroes and villains, she might find Deku's transformation interesting. She could provide some of her unique skills, like shape - shifting, to help Deku in his villainous plans. Additionally, Twice might also join them because of his loyalty to Toga and his own sense of being an outcast in the hero world.
A possible plot is that Villain Deku has a plan to destroy a major hero institution, and Hero Deku has to stop him. But when they meet, Hero Deku realizes that Villain Deku was once like him, full of hope. This makes Hero Deku hesitant to fight at full force. Or perhaps Villain Deku has kidnapped someone close to Hero Deku, and during the rescue mission, Hero Deku tries to convince Villain Deku to change his ways. Also, they could be from alternate universes where the roles are reversed, and they are forced to interact and learn from each other.
For Hero Deku, his development could be shown by how he reacts to seeing his dark self. He might start to question his own beliefs and actions. For Villain Deku, his development could be in the form of a possible redemption arc. Maybe he starts to see the error of his ways through his interactions with Hero Deku. For example, if Hero Deku shows him kindness or understanding that he never received before.
Interesting plot ideas in My Hero Academia Female Deku fanfiction can be diverse. For instance, Female Deku could be mentored by a female pro - hero who has a very different approach to heroics compared to the male heroes in the series. This could lead to her developing a unique fighting style. Another idea is that she gets involved in a tournament where the rules are designed to disadvantage female heroes, but she finds a way to turn the tables. Additionally, a plot where she has to rescue male heroes who underestimated her because of her gender could be both empowering and full of action.