The stuff that really got me lately isn't actually the super high-kudos epics. There's this one by ArgylePirateWD called 'Thermodynamic Equilibrium' that just... clicks. It takes the whole 'brilliant minds' thing and pushes it into this quiet, tense space where they're trying to fix the Support Department's budget allocation formulas, of all things. The romance is all in the margins, in how Momo misinterprets Izuku's muttering as criticism until she realizes he's just working through a problem aloud, and in how he sees her blueprints not as perfect finished products but as a living conversation. It's slow, it's technical, and the emotional payoff is them finally agreeing on a variable. Sounds dry, but it captures that specific joy of being understood on your own weird wavelength.
I'd argue the fandom sometimes misses the mark by making Momo just rich or Izuku just heroic. The best fics dig into their shared insecurity—hers being performative, his being internal—and how they might actually soothe that in each other. 'Cartography of a Smile' by tidalLullaby does this through letters they write but never send during the war arc, found after everything. The prose is aching and beautiful, less about grand declarations and more about the weight of a pen in your hand when you're describing your fears to the one person you think might get it.
Honestly, skip the ones where they're already a couple in the summary. Half the fun is the glacial pace of two incredibly smart, incredibly dense people figuring it out. Look for tags like 'mutual pining', 'teamwork', 'strategy & planning', or 'emotional constipation'. AO3's tag system is your friend here. The quieter stories in that vein tend to have the most re-read value for me.