Mirai Nikki

Second year middle school & 14 year old, Amano Yukiteru, is a boy who has a problem with making friends. He keeps a diary on his cell phone of the things he witnesses, believing himself to be a bystander to the world's happenings. His only salvation from solitude are his imaginary friends, one of which turns out to be not so imaginary, Deus Ex, an apparent lord of time and space. Deus tells Yukiteru he's planning a 'fun game' and upgrades his cell phone to a new model which predicts the future. Yuki is quick to abuse this power but is brought back to earth when the diary predicts his own death. After managing to off his would be murderer Yuki discovers Deus's game involves himself and eleven others with precognative diaries using their new powers to fight to the death for an incredible prize going to the last man standing. Outgunned and desperate to survive, Yuki teams up with Gasai Yuno, his psychotic stalker who'd do anything from killing for him to dying for him.