Enji Todoroki fanfics? Oh, you're speaking my language! If you're after those spicy reader-insert stories, Archive of Our Own (AO3) is basically the holy grail. The tagging system lets you filter for exactly what you want—just search 'Enji Todoroki/Reader' and use the 'Explicit' rating filter. I've stumbled upon some real gems there, like 'Scorched' where the tension builds so slowly you practically sweat through the screen. Tumblr also has hidden treasures if you dig deep enough, though you might need to navigate through moodboards and headcanons first.
Wattpad can be hit-or miss, but I once found a surprisingly well-written arranged marriage AU under all the clichés. Just brace yourself for occasional typos mid-steamy scene. And if you're into Japanese doujinshi, Fantia or Pixiv might have what you're looking for, though the language barrier can be tricky. Personally, I love how AO3 writers explore his complex personality—way beyond just 'flame hero daddy energy.' Some fics even weave in his guilt about the family drama, which makes the romance hit different.