Quirkless Deku AU in which, after All Might tells Izuku he can't be a hero, Izuku takes the words to heart and decides to completely cut heroics out of his life, so he isn't reminded of his failed dream. He doesn't have any social media and doesn't read news articles about heroes. If a hero is mentioned on tv, he turns it off. He buys the same, non-sponsored groceries all the time, and he forks out the extra money to go ad-free on things like YouTube, so he never sees them in commercials. We know he's a thorough person, and he applies those skills, avoiding heroes to an impressive extent and just focusing on whatever new career path he set his eyes on (Maybe botany? But this isn't just like, basic flower shop AU. He's super smart, so my boy is probably breeding award-winning new species of orchids or some shit.)
As such, he ends up being probably the only person in Japan who has never heard of Todoroki Shouto.
They have some sort of meet-cute, and at first, Shouto can't figure out why this guy is pretending not to know who he is (is he trying to be polite, pretending Shouto is normal??), but eventually he realizes Izuku legitimately has no clue who he is, and Shouto is soooo enamoured, because Izuku is so nice and seems genuinely interested in him, and for the first time, Shouto knows it's all sincere and not someone trying to get close to him because he's famous. He becomes desperate to keep his profession a secret, leading to some comically close calls. But the longer it goes, the harder he falls, and Momo keeps insisting he has to tell Izuku the truth because he can't enter a serious relationship with this huge lie between them. But just when he's about to fess up, something happens that makes it clear to him that Izuku isn't just out of touch with popular culture, he is /actively/ avoiding heroes and dislikes hearing about them, which makes Shouto think he'll stop talking to him, and he doesn't know what to do, and now Jirou is helping Momo scold him, and he's so stressed.
Of course, the boys don't realize they know someone in common. Bakugou somehow lets the cat out of the bag, not knowing Shouto was keeping his heroics a secret. (Back to botany...maybe instead of orchids, Izu specializes in poisonous plants? And a new poison is involved in some sort of crime, and the police want him on as a consult, and Bakugou ends up involved on the heroics end of things, leading to a reunion with Izuku who he hasn't seen since middle school. Somehow Shouto comes up in conversation while they're working on the case.)
And then it all goes to shit, Idk what happens next. Izuku is more upset about being lied to than Shouto being a hero, and Shouto has to prove he wasn't just messing around. I feel like there's a scene in there where Izuku cries on his mom's lap, and Shouto gets an earful from her. They make up, of course, and start dating. Since this is one of my ideas, they probably get married in the epilogue.