Yukiteru always rejects offers to go out with friends, preferring to spend the time writing a diary on his cell phone. He has what he believes is an imaginary friend called Deus Ex Machina. However, one day Deus asks him to play a survival game along with eleven others. The winner becomes the next Deus Ex Machina. In order to win, the contestants must use their diaries of the future to eliminate one another. For Yukiteru to survive, he must team up with another diary holder, a girl named Yuno.