So, focusing on plot ideas beyond just 'they're both lonely outcasts,' which is the default and honestly a bit tired now. What about a body-swap scenario? Like, during a chaotic quirk accident, Izuku and Himiko end up stuck in each other's bodies. The tension isn't just from the obvious shock, but from them having to navigate the other's social circles and responsibilities. Izuku trying to curb Toga's instincts from inside her own head, while she's gleefully (and disastrously) trying to be a 'hero' in his. It forces a weird, intimate understanding neither asked for.
Another angle I rarely see is a straight-up 'what if' where they meet as kids, before UA. Maybe Himiko's family moves next door. A friendship forms that's completely separate from heroes and villains, built on shared weirdness—his notebook obsession, her fascination with blood. Then the canon timeline hits and they're on opposite sides, but that childhood bond creates a tragic pull. It's less about romance initially and more about a foundation that makes their later conflict heartbreaking.
Or flip it: make it a deliberate, strategic alliance. Izuku, post-war, ends up leading some kind of rehabilitation initiative. Toga is his first or most difficult case. The plot revolves around sessions, deprogramming, trust-building exercises. The relationship develops from there, slow and fraught with professional ethics and past trauma. It's a quieter, more psychological take than most action-packed fics.