Second year middle school student, Amano Yukiteru, finds it difficult to make friends. He only thinks of himself as a bystander, just someone who watches the world go by, writing down everything he sees in his cell phone diary.

Tormented by solitude, Yukiteru begins to imagine things like a friend called Deus ex Machina, who is apparently the Lord of Time and Space. Seeing Yukiteru's miserable state, Deus gives him a new ability. His diary now spells out events that will happen in the near future, updated daily, for the next 90 days. This gift inadvertently forces Yukiteru to participate in a game where the winner . the last one alive . will become Deus' successor. Should Yukiteru lose the diary he will be dead, and there are quite a few other scrupulous players participating in this very deadly game.