A string of mystifying deaths has been taking place, in which individuals are torn apart without explanation. The situation intensifies when Homura Kei's computer class of 36 becomes prey to the violent onslaught. Because Kei is prone to cutting classes, she is inexplicably the only survivor of the horrific massacre. Later on, Yuon, a hacker, arrives at her doorstep claiming to have lost a loved one and possessing classified intel. The presumed perpetrator employs a program that portrays a blue butterfly on a screen that has fatal effects on human conduct. Kei and Yuon must join forces to track down the culprit before it's too late.
