1x12 - Who Killed Daigoro Tokuyama?

The day of the school festival. The students are tired from the preparations and have fallen asleep. They give up trying to make it in time, and cancel their haunted house. Then, as someone comes in, numerous "ghosts" appear and surround the person. One ghost reveals herself to be Yurina Hirate, and she unravels the mystery of Tokuyama's death. So, who killed Daigoro Tokuyama?