Anna Nagata

In the future, the Japanese government captures a class of ninth-grade students and forces them to kill each other under the revolutionary "Battle Royale" act.

People mysteriously start receiving voicemail messages from their future selves, in the form of the sound of them reacting to their own violent deaths, along with the exact date and time of their future death, listed on the message log. The plot thickens as the surviving characters pursue the answers to this mystery which could save their lives.