A Classroom Bereft of Angels

There's something unusual about my class. Our beautiful and perfect angel classmate, Amane, just died. That's why everyone is doing a “funeral” for her. Everyone seems to be scared but did not say anything. I'm sure they are hiding something. After all, before she died, Amane said something strange. Hey, don't tell me, there are traitors among us? Well, let's hold a “class meeting”! No one should ever leave the room before we know who's behind this...