Another

Apathetic school
ghost with a bad memory
case of the cursed class.

Despite I knew the main twist thanks to those people who like to spoil books, I was surprised by the story in general. I know it's kinda frustrating at the beginning because nobody says anything to Sakakibara, but the mystery unfolds in a very good pace, so I'm satisfied overall. Ayatsuji Yukito has gained another fan! I hope to get more of his books.