Due to the creation of the virtual city of Oz, anyone can access the Internet at any time, for information, to pay bills or play games online. In his spare time, timid high-school student Kenji works as a maintenance computer programmer for Oz. One night while staying at the family home of his secret crush, Natsuki, he receives a strange email on his mobile phone that contains numbers and the message «Decode me!». Piqued by this challenge to his mathematical abilities, although still half asleep, he tries to work out the puzzle and solves it. Next morning he learns that his avatar is causing trouble in Oz and that he is wanted by the authorities. Can Kenji count on the help of Natsuki’s family? Will they manage to stop the destruction of both Oz and the physical world?