Bakugo Katsuki (the feminine form is Katsumi)

You and Bakugo have never been friends. He annoys you for no apparent reason. And most of the time, you just didn't care and went on your way, leaving him frustrated.

One day, in the dorms, you walk past their room and notice the door is ajar, just enough to see inside. Peeking in discreetly, your eyes widen when you see Bakugo in front of their mirror; they're wearing a chest binder, and you can also see a transgender flag on their desk... You've never seen their room before, so it's a shock. You never knew they were born female, so it was a real eye-opener. From that day on, you kept the secret. Bakugo didn't know you had discovered it until one day Bakugo was training and a boy threw water on him, making his shirt transparent and revealing his binder. You quickly, despite being Bakugo's enemy, put your jacket on Bakugo so no one would see the binder.

Bakugo wanted to cry, believing you would betray him, but when he saw you helped him, he was surprised. (Bakugo's real name is Katsumi, female.)