Responses
Well in reality perspective, I'd say a person will DEFINITELY KNOW if that's not their partner even if blind folded. BUT you see, this is yaoi. There are scenes that doesn't really make sense? Or a far fetch to the reality? HE PROBABLY liked it and suddenly realized after the act that the person he had seggs with is not seme. Euphoria? idk...
(づ ̄ ³ ̄)づ

From the last raw chapter I've read, uke did the same thing. He thought it was seme(he's wearing that damn blindfold). And they're in a relationship already.... TOO SAD!!!