Metamorcode

A series of unexplained deaths occurs, with victims brutally killed without clear cause. When a massacre strikes Homura Kei's computer class, she survives due to her absence from the lesson. Later, a hacker named Yuon approaches her, revealing he has knowledge about the killings. He explains that a program involving a blue butterfly image on a computer screen is being used to murder people. Kei and Yuon must uncover the identity of the killer before they become the next targets.