Yukiteru Amano, a reclusive middle school student, is drawn into a brutal survival game orchestrated by Deus Ex Machina, the god of space and time, where the winner inherits Deus' unlimited power. All 12 participants, including Amano, are habitual diary keepers, but with a twist: each diary has been transformed into a "Future Diary" that predicts the future to varying extents. Amano holds a "Random Diary" on his cellphone, which provides precise descriptions of his surroundings. Though hesitant to fight, his desperation to survive drives him to ally with his classmate and fellow diary holder, Yuno Gasai, an attractive girl with a strange obsession for Amano. As this bloody battle royale unfolds, shocking revelations emerge, altering the very nature of this twisted game.