Unfortunately it is possible. Alcohol can make people completely disoriented. When he's drunk, like a lot of people, he's probably thinking the most about his boyfriend. You're drunk as hell, your vision is blurred, you're only thinking of your man, and you see a shape that looks like your man? Drunk Logic dictates that's your man. Sex can also sober people up pretty quickly so that's probably why he was only able to start being aware of details like how the ceiling look during his creepy professor's assault.
Wowwww informationnnn
Interesting hmmm then why many couples break up because of a cheating during being drunk ,, I think in real life the seme will never believe him since he didn't know the truth like us but well this is a yaoi so they will propaply end up together although a uke should not go to a stranger house after drinking even if that one was his teacher,, I'm not blaming the uke of course just saying he wasn't careful
I'm wondering how come he was that drunk that he was not aware he is sleeping with someone else,,, is that even possible