The social network OZ has become the largest network in Japan and controls most of the country’s infrastructure. Kenji Koiso and his friend Takashi are working a part time job on OZ when Kenji’s high school crush Natsuki asks him and his friend if one of them would work for her during the summer when she goes to visit her family. Kenji ends up joining Natsuki unknowing that she has already told her family that she was engaged and that she really hired Kenji to play the role of her fiancé.
One night when visiting Natsuki’s family Kenji is text messaged a math puzzle which is actually the encryption for OZ. Kenji being the math genius he is breaks the code in just 1 night and instantly OZ is thrown into chaos as a hacker takes over the social network causing Japan’s infrastructure to collapses.