internalized misogyny
Fem!Deku internalizing the idea that females cant be good heroes and feeling confused so she tries to pretend to be a boy.
Katsuki catches her trying to bind and he surprises her: “Are you a boy or a girl?”
“Girl...?”
“You dont sound too sure. Because if you're actually a guy that's definitely valid, you dont have to worry.”
Izuko though is insistent, “I'm a girl”
She's happy being a young woman but she just wish that there were more female heroes who were saving people more like AM. “Then why are you pretending?”
“Because girls cant be heroes!”
“Ha!? Who thr fuck says that, if you weren't such a Deku you could be a fucking hero!”
And that kind of emboldens Izuku, that she can be girly and still a hero and she owns it.