1x11 - Who Killed Daigoro Tokuyama?

The evening before the school festival, the janitor Hashibe shows Yurina Hirate a DVD. Neru Nagahama takes it, just to see that it's been broken. It's the confiscated DVD that Tokuyama gave to her the day he was killed. The class had watched it before, but they'd seen nothing suspicious. Who did it? Meanwhile, they find out who'd been sending the messages.