The Samejima Incident.

Every year, Nana Sasaki and her former classmates hold a reunion of their high school music club. This year, the reunion is being held online. However, one of them, Ayumi, doesn't show up. When the others voice their concern, Yuki and Suzu reluctantly tell them about the Samejima Incident, an urban legend which circulated on the internet 20 years earlier. Those who find the truth about it become cursed and die. As Nana and the others start to panic, the real horror begins.