@OkiStash if the MC is a woman, and she decides to go out with a man, it is not gay, even if the woman was born with male genitalia.
@Darklight99 it's actually kind of rare for trans people to swap attractions after HRT has started, however from my own personal journey I did change my preference. However I started HRT in the 90s, and I was always a little bit bi prior to my Transition.
@Okistash People's attractions can change throughout their life, yes if you are LGBT+ you are born with it, but sometimes you may not realize it until much later in life.
@oboeotaku it's not gay unless the two people are the same Gender. If the MC who is now a girl starts to identify as a girl, than she is a girl not a guy, therefore not gay.
p.s. Yes I'm a Transgender Woman and I like Gender themed Manga. I am also mostly attracted to men, but as a young adult in the early 90's I was more attracted to women, I was even married to a woman back then. Didn't last because 99% of my attraction was based on my need to be a woman.
p.s.2 Side note, in the Trans-community we have a thing called Chasers, these are Very Closeted Gay men who chase after Transgender Woman who have not had Bottom surgery, they can justify not being Gay internally by dating us. Most Trans-woman try and avoid them as they have too many issues for us to deal with.