Well, in such a fanfiction, it often explores a different side of Deku being a villain and his relationship with Todoroki. It could be about how their dynamic changes from the original story. Maybe Deku as a villain has different motives and goals that somehow involve Todoroki, like trying to use Todoroki's power for his own evil plans or trying to turn Todoroki to his side.
I don't encourage seeking out 'lemon' fanfiction which often contains sexual content. But if you want to explore the relationship between Villain Deku and Todoroki in a more appropriate way, you can join fan forums and ask other fans if they know of any well - written stories that focus on their dynamic, be it a more adversarial or a complex relationship that doesn't involve adult themes.
Power imbalance is often a theme. Deku might gain new, more dangerous powers as a villain, and Todoroki has to figure out how to deal with that. There could also be a theme of trust. Since Deku is a villain, Todoroki has to decide whether to trust him or not. And if he does trust him, it could lead to all sorts of complications in the story.
The 'deku texting story' could potentially revolve around Deku's internal thoughts and struggles as he communicates with others via text. Since Deku is often seen as a determined and kind - hearted character, the texting story might showcase his efforts to support his friends, like when they are facing difficulties in their hero studies. It could also depict how he uses texting to get advice from his mentors, such as All Might. Through these text exchanges, we might get a deeper understanding of Deku's character growth and his relationships in the story world.
In the 'deku texting story', Deku is the central figure. However, considering his world in My Hero Academia, other characters who could play major roles in the texting story are numerous. His friends from Class 1 - A would be prime candidates. They are constantly interacting with Deku in the original series, so it makes sense for them to be in the texting story. Additionally, any heroes or sidekicks that Deku looks up to or works with might also be main characters. Their wisdom and experience could be shared through texting, and they could offer guidance to Deku during his journey to become a great hero.
To write this fanfiction without the 'lemon' aspect, think about their backstories. Deku's fall into villainy could be due to some great betrayal or a different view on hero society. Todoroki might be on a mission to either save or stop Deku. You can build a story around their ideological differences and how they interact with each other. For example, they could have a series of battles or encounters where they gradually understand each other more.
The theme of self - discovery is also prevalent. Both characters grow and learn more about themselves through their interactions. They discover new aspects of their powers, emotions, and identities as they navigate their relationship in these fanfics.
Another theme is cooperation. Given their different quirks, fanfics often explore how they can work together effectively. Like in a battle scenario, Momo can create useful items and Todoroki can provide offensive and defensive power with his ice and fire abilities.
One common theme is redemption. Since Endeavor has made many mistakes in the past regarding his family, especially with Todoroki, many fanfics focus on him trying to redeem himself. Another theme is forgiveness. Todoroki has to decide whether to forgive his father or not. And also, family bonds. They are father and son, so exploring how they can strengthen or repair their family connection is often seen in these fanfics.