and the trope of "I didn't know I liked men before I met you". Bitch. You don't need to fuck a man to be attracted to them. If a 40 years old man tells you that he didn't know that he liked men before he tried it out, he lies through his teeth. You can deny the attraction but it will still be here, even if you don't fuck.
I hate it too. There's also this I am only gay for you trope. Tbh the only manga that addresses bisexuality properly is therapy game.
As a bi person it annoys me so much! There's a time and a place where it CAN work, i.e. if the character was forcing themselves to be in relationships with girls and couldn't figure out why it wasn't working or if they never had any interest in girls to begin with and so they just assumed they were straight cause... you know, comphet. But otherwise......
Picrew : you and your gender bend