What is happiness? As a psychology enthusiast, high school student Ritsu Shikishima enjoys pondering such questions while spending his tranquil days with friends. However, his perfect world starts to fall apart when he hears a strange voice, obscured by static, begging for help. This voice belongs to μ, a beloved pop idol, whose singing begins to have a detrimental effect on the world. Right before Ritsu's eyes, the faces of his friends and family become distorted by glitches as the sound of μ's voice transforms them into Digiheads: berserk monsters dedicated to exterminating anyone who begins to awaken to the true nature of their existence. Realizing that he is trapped in a virtual world created by μ called Mobius, Ritsu must now gather everyone else who has managed to realize the truth before they are all eliminated. Together, they will use their newfound powers and weapons granted by their emotions—known as the Catharsis Effect—to fight off the mysterious group known as The Ostinato Musicians as they struggle to escape.