Caligula

Ritsu Shikishima, an avid student of psychology, lives a seemingly ordinary life with his friends in a high school setting. However, his world is disrupted when he discovers a mysterious voice from μ, a popular pop idol, whose songs have an unusual side effect: they transform people into Digiheads, violent creatures driven by a distorted sense of reality. Ritsu soon learns that he is trapped in Mobius, a virtual world created by μ.