I'm not sure exactly what (or which couple) you're referring to, but I think switching roles is a lot more common than people think. It's just kind of the norm to have a strict top and strict bottom in a lot of relationships, and that shows in BL.
erm u mean the highschool cosplay scene? no he was erm top riding his semeXD ?cowgirl ?
Honestly me myself i don't even get what am i being confuses in the first place.....bc i forgot what i'm being confused of about the seme uke role.....sorry
So the uke will switch the role with the seme in the future? He will be the seme?? In the future???????..........ummmmmmm