The Future Diary (2011)

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Yukiteru Amano, a solitary teenager, fills his days by jotting down thoughts in his mobile diary and chatting with his imaginary friend, Deus Ex Machina. One day, he discovers that his diary has already been completed for him, and the events described begin to unfold in reality. Deus reveals himself as a genuine deity and warns Yukiteru that losing his diary would mean his demise. As Yukiteru learns to leverage the diary's power, he encounters Yuno Gasai, a devoted stalker who also wields a Future Diary predicting his death at the hands of a serial killer, another diary holder. Together, they manage to thwart the killer, with Yuno assisting Yukiteru in eliminating him. Following this, Deus lays out the survival game’s rules to Yukiteru and the other diary owners, where they must eliminate one another for a chance to inherit his powers.