Isn't this low key biphobia?

Hi I’m bi myself (or pan I’m not sure)! But for some reason I never thought of this as biphobia. And I don’t think it’s because there aren’t any bi people in Japan or Asia but I think because of the common stereotype/problem(?) of homophobia. I mean, like it was in the manga if you even say you like men you’d be labeled as fag before you could even discover if you like both men and women or just men. But to me in this manga the thing about Kawai being straight would still be there if he was bi, because the problem was that Ohara believed he would (in the end) choose a woman (to maybe fit society’s norms or make his parents happy) over him.

Hi! Another bisexual here, I never thought of this kind of topics as biphobia, and the reasons behind this are two:
- The romantized concept of "I don't like men, I just like you", which it makes the relationship or feelings "more special".
- The lack of general knowledge on bisexuality per se, from the general population, which includes our beloved mangakas in some cases.

Which is why did said low key instead of just outright, but still, just because people don't know about something doesn't mean the problem isn't there right? They're doing something that's maybe kinda sorta offensive, it's just they don't know that they're doing it

Late comment here but I'd say that back when this story was released (2014), bisexuality wasn't very well known in East Asia. People only knew straight and gay, and they threw trans people into the gay section carelessly too. It's not until, I'd say 2018, 2019ish that awareness for the other letters in LGBTQ+ got slightly better here, you can see that many recent manga/manhwa have bi people in it or they stop with the "straight man who fall in love with a gay man" shtick.