Yukiteru "Yuki" Amano is a loner who spends his time texting in his cellphone diary, playing darts and talking to his imaginary friend, Deus Ex Machina, the God of Time and Space. One morning, he finds his diary entry for the day filled in already, and the events recounted in the diary strangely start coming true. Yuki is then startled upon learning that Deus is an actual deity, who reveals to Yuki that his diary can now predict his future, but also warns him that he will die if his diary is destroyed...