Archive of Our Own is the undeniable central hub for Tadano x Komi content. The tagging system makes finding exactly what you want a breeze, whether it's fluffy coffee shop AUs or more speculative post-canon explorations. I've found that the writers there often have a really strong grasp of the source material's tone, balancing Komi's social anxiety and Tadano's earnest support without making them caricatures.
What sets AO3 apart is the sheer volume of high-quality, completed multi-chapter fics. You can sort by kudos or bookmarks and find stories with thousands of engagements, which gives you a good sense of community favorites. The comments sections on popular works often turn into mini-discussions about character nuances, which is half the fun.
I'd say FanFiction.net still has a dedicated, if smaller, pocket of writers for this pairing. The interface feels older, but some authors who've been writing for years prefer to cross-post there. You might stumble upon some real gems that never migrated over to AO3, especially from the earlier days of the fandom.
Wattpad has its share too, but the style tends to lean more toward the younger reader demographic—lots of reader-inserts or high school drama tropes that diverge pretty heavily from the original manga's vibe. It's not my personal preference for this ship, but I know some people enjoy those twists.
I occasionally check Tumblr for shorter drabbles and headcanon threads. The tagging system there is chaotic, but when you find a writer who consistently posts good snippets, it's like striking gold. The reblog culture helps the best ones circulate widely.