One common theme is possessiveness. Since Todoroki is yandere, he often wants to keep Deku all to himself. Another theme is the struggle between Deku's own agency and Todoroki's overbearing love. For example, Deku might want to pursue his hero career and have other friends, but Todoroki's yandere nature tries to limit that. Also, there's the theme of secrecy. Todoroki may try to hide his yandere tendencies from Deku and others at first.
Often, the theme of growth is present. Deku is constantly growing as a hero, and Midnight could play a role in that growth, either by inspiring him or directly training him. And there could be a theme of the unlikely pair, as they are quite different in age and personality, which makes for an interesting dynamic in the fanfics.
One popular Midnight x Deku fanfic might be 'Midnight's Guidance'. In this fanfic, Midnight could be portrayed as a mentor figure to Deku, guiding him in ways that are different from his regular teachers at UA. She might use her unique quirk knowledge to help Deku enhance his own quirk.
Sure. There's a fic called 'Yandere Shoto's Desire'. It shows how Todoroki, with his yandere nature, would go to great lengths to protect Deku from any perceived threats, even if those threats are just Deku's other friends. It really delves into the darker side of his love for Deku. Also, 'Dark Love of Todoroki' is a fic that has Todoroki's yandere side emerging slowly as he falls deeper in love with Deku, leading to some very interesting and somewhat disturbing situations.
Some Tumblr blogs also focus on My Hero Academia fanfics. Look for ones that are dedicated to Deku or Midnight. They may have curated lists or even their own original 'Deku x Midnight' fanfics. It's a matter of exploring different blogs until you find something interesting.
You can try Archive of Our Own (AO3). It has a large collection of fanfics, and you can easily search for Midnight x Deku fanfics using the search function. Just type in 'Midnight x Deku' and it'll show you relevant results.
One common theme is the power dynamic. Given that Midnight is an established pro - hero and Deku is an up - and - coming hero, there can be a lot of exploration of how power plays into their relationship. Another theme could be mentorship turned into love. If Midnight was initially Deku's mentor in some way, the story could be about how that relationship evolves into something more intimate.
One aspect of deku and midnight love fanfiction could be exploring their relationship in an AU (alternate universe). Maybe in a world where Deku isn't just a student but an equal hero to Midnight, and their relationship develops from mutual respect to something more romantic. They might go on adventures together and discover new feelings along the way.
In yandere x reader fanfics, yanderes usually display intense emotions. Their love for the reader is not the normal kind; it's more of an obsessive love. They may have a dual personality where they can be extremely sweet and loving one moment, but if they feel threatened in their relationship with the reader, they can turn very dangerous and menacing.
In a yandere phobos x will fanfic, one aspect to consider is the power dynamic. If Phobos has more power, it can intensify his yandere tendencies. For example, he could use his influence to isolate Will. The fic might also focus on Will's reaction to Phobos' yandere behavior. Will could either be scared or, in an interesting twist, gradually come to understand and even accept Phobos in some way.