MHA x Umamusume fic idea I've been playing with lately.

Fem!Izuku, or rather, Green Valley, is an Umamusume. She's born to run as every other is. But that's not what she wants.

Umamusume have existed before quirks appeared, and they have ran forever, but with the Dawn of Quirks, one thing was clear, Quirks were for Humans, all Uma Musume were naturally quirkless.

Green Valley wants to be a Hero instead of a Racer, go to U.A. rather than Tracen. She's good at running but she still isn't as strong as a regular quirked Human.

Eventually, plot happens, and when Green Valley saves Bakugou from the Slime Villain, All Might decides to take a gamble and assumes One For All will still be able to be passed to an Umamusume, considering he was quirkless before. So she's the first Umamusume with a quirk and going to be a Hero.

Maybe you could give her a neighbor or some family/friend that goes to Tracen so U.A. would have a way to interact with it. I'd like to see interactions like Tachyon and Hatsume, or Goldship and Aoyama.

At some point, we see a second quirked Uma, Little Horn (Eri) who has a horn in her forehead.