I've noticed a lot of readers find the Iida and Todoroki pairing sparks from their contrasting yet complementary natures. Stories often start with their shared status as class reps, that foundation of responsibility and mutual respect. A really common theme is the 'strict rule-follower meets the emotionally reserved heir,' where Tenya's rigid adherence to structure slowly, almost painfully, helps Shoto navigate the complexities of social interaction he missed in his childhood. It’s rarely about loud declarations; it's more about Iida noticing the slight changes in Todoroki's expressions, or Todoroki quietly supporting Iida's ambitions in a way that doesn't require grand speeches. The engine-leg quirk and ice-fire quirk dynamics also get interesting metaphorical treatment—stories about overheating and cooling down, or finding a balanced rhythm together.
Another trope I see a lot is the post-injury or vulnerability arc. After the Stain incident, there's fertile ground for exploring Iida's trauma and his perceived failure of his heroic ideals. Todoroki, having his own history with family legacy and anger, becomes an unexpected anchor. He doesn't offer platitudes; he just stays present, which is exactly what a guilt-ridden Iida wouldn't know how to ask for. This can flip, too, with Todoroki dealing with the fallout from his family drama and Iida offering steadfast, practical support through scheduled study sessions or training, his way of showing care.
Slow-burn academic rivals to lovers is another favorite, though it's less about outright rivalry and more about two high-achievers pushing each other. They might compete for top grades or analyze each other's battle techniques with an intensity that gradually bleeds into something softer. Family expectations are a huge theme—the weight of the Iida name and the engine legacy versus the crushing shadow of Endeavor. Fics explore them building something new together, a partnership or relationship defined by their own choices, not their family histories. I just finished one where they started a joint project on quirk ethics, and the way their late-night research sessions evolved felt incredibly true to their characters.