How do I phrase this..
You can "not be attracted" to someone physically because of their gender, but still want to have sex with them because you are attracted by other qualities or you're just horny.
Basically the whole "I'm not gay but I like you" line you see in many yaoi. These people would technically be bi or demi sexual, but not gay.
As far as tags go though, it usually means the uke/seme start out presenting as straight.
Lol! I think what it means is that they were previously exclusively straight (aka heterosexual) and then they fell in love/have sex with the same sex...
Or it could be that they're just exclusively a top or a bottome. They don't switch or they can't do both....
The truth is that those comics are written by and for women, and they usually like straight men. It is kind of a marketing thing, like "I can be yours, my lady, so you can worship me, but the story is great because my love surpased the boundarys of gender, so you can love me even more".
When I read those lines saying "I am straight, but I love you anyway", my head just skips them so I can keep reading without rolling my eyes to the back of my head.
I'd agree on them being a demisexual or bi but gosh just the terms (straight-uke/seme) freak me out a bit ngl
ahaha... reminds me of that one (cursed) YOI dj where the author flat out denied Victor and Yuuri being in love, and that it grossed her out... and yet still made a MxM pron about them... ahaha,,,, =_=''
Now I'm curious. Do you have a link to that dj?
why there's tags like 'straight-uke' and 'straight-top' ? in BL stories... It kinda reminds of that post on tumblr that said "I sleep with men, since I TOP it's not gay" which makes me go
(O.o)? excuse me, wut?