The pairing's really built around a specific flavor of dynamic, that stoic strength hiding vulnerability with the brash hero who's more wounded than he lets on. It's not universally covered on the big archives.
I've found the most consistent quality for that dynamic on Archive of Our Own, no question. The tagging system lets you filter meticulously—you can combine 'Hawks Takami Keigo', 'Fuyumi', and 'Todoroki Family' tags, then sort by kudos. That weeds out the one-off crossovers and gets you to the core character studies. I'd avoid FanFiction.net for this; the categorization is too broad, and the tagging is primitive, so you'll sift through endless fics where they're just background for Shouto-centric plots.
There's also a surprising pocket on Twitter/X, believe it or not. Writers will post threadfics with the #bhna or #mha tags, and some of the most poignant, short-form explorations of their 'what could have been' scenarios live there. It's more ephemeral, harder to search, but sometimes the rawness in those threads hits differently than a polished AO3 chapter.
The key is remembering this isn't a top-tier popular ship, so you have to hunt in the corners. Don't just browse the main pairing tag; look for authors who write complex Todoroki family drama, then check their bookmarks. They often curate the good stuff.