Interesting- so bro is some degree of international slang! Assuming that you did mean Japanese and not French in that last part, it makes sense, at least from my narrow realm of experience in My Hero Academia fanfiction, with some characters, particularly Kirishima, referring to each other as bro.

I don't remember off the top of my head if it's present much in the English dub of the show, but it's become relatively accepted fanon practice that Kirishima calls his close friend Bakugou 'Bakubro' and sometimes tries to fit bro in the names of his other friends if the fic involves them becoming better friends, i.e. 'Todobroki' for Todoroki, 'Midoribro' for Midoriya, and I've sometimes even seen 'Brochako' used to address the female character Uraraka Ochako. IDK how present it actually is in the original Japanese or non-English fanworks, so ymmv, but that's just what I've seen.