On my first playthrough I managed to find the impostor after (what feels like) a 10 minutes of questioning. I was very proud of myself btw. But then when I exited the door I found out there were supposed to be 2 impostors. Oh...
On the next playthrough, I found that some of their answers were different than before. And sure enough they were the imposters. I realized this has turned into a spot-the-difference game!
I think it's a clever way to fit the impostor concept into a short game format. Well done!