Alright so diving into the Inosuke/Aoi tag is kind of a wild ride because there's not exactly a mountain of it—they're a side pairing at best in most people's eyes. But that scarcity means when you find a good one, it really sticks with you. I stumbled across this one on AO3 called 'Silence and Thunder,' which just nails their dynamic. It's all about Aoi trying to teach Inosuke basic manners and herb lore, and him being his feral self, but the writer doesn't force the romance. It builds from this grudging respect into something quiet and real.
Another one I'd throw out there is 'Breathe,' which is a post-manga, slice-of-life thing. It deals with Inosuke's recovery and Aoi's caretaking without making her just a nurse trope. She's got her own frustrations and backbone. The author understands that Aoi's strength is in her steadfastness, not in flashy battles, and Inosuke's gradual, confused appreciation for that feels earned. Sometimes the shorter fics in this tag work better because they focus on a single moment or observation instead of trying to build an epic plot where none exists in canon.
The tag can get clogged with stories where they're just a background pair in a bigger Tanjiro/Shinobu or Zenitsu/Nezuko fic, which is fine but not what you're after. Filtering by the relationship tag and then sorting by kudos usually surfaces the standalones worth your time.