Yukiteru "Yuki" Amano is a loner who spends his time writing in his cell phone diary, playing darts and talking to an imaginary friend, the "god of time and space" Deus Ex Machina. One morning, he finds his diary entry for the day has been filled in already. Stranger yet, the events recounted in the diary start coming true. Deus, who reveals he is an actual God, warns Yukiteru that if his diary is destroyed, he will die. As Yuki starts using the diary to his advantage, he is approached by a stalker named Yuno Gasai who also possesses a Future Diary cell phone that foretold his death at the hands of a serial killer, himself another Future Diary owner. Yuno helps Yukiteru evade the killer and enables him to hit the killer's phone with a dart, which causes him to vanish into a vortex. Afterwards, Deus explains the rules of the survival game to Yuki, Yuno and nine other diary owners; they must try to kill each other in order to win the right to succeed him.