Been looking around for these for ages, and it's honestly tricky finding stuff that really clicks. A lot of the fics feel like they just drop Ichigo and Yoruichi together because it's a cool pairing on paper, without really digging into the weird, hilarious, and oddly tender dynamic they actually have. You know, the banter, the sparring, the whole mentor-student thing turned sideways. That one where she drags him to the living world for undercover missions and they have to pretend to be a couple? The constant bickering over takeout choices felt more in-character than half the epic-war plots.
I'd say skip anything that just makes her a generic 'cool girlfriend' or turns Ichigo into some super-smooth operator overnight. The best ones let her be mischievous and older and infinitely more experienced, while he's still stubbornly, endearingly himself. There's a short piece on AO3, can't remember the title, where he just... fixes her sandal after a fight without making a big deal of it, and she's quietly floored. It's small moments like that, not grand declarations.