Anyone can easily use public services such as e-mail, e-wallet, and intelligence search wherever they are, and a virtual city like reality has been built and spread to all corners of the world. The protagonist Koiso Kenji is an introverted science boy. During the summer vacation, he was dragged by his senior, Shinohara Natsuki, to her old man, Nagano Prefecture, うえだし. There lived the Sengoku family, the Jinai family, that had existed since the Muromachi era. Led by Xia Xi's 90-year-old great-grandmother, doctors, fishermen, firefighters, plumbers, electrical store owners, police officers, officers of the Self-Defense Forces, elementary school students to babies, and relatives from all walks of life. During the summer vacation spent in this lively farmhouse, Kenji saw the activity and harmony of the Jinuchi family. One night, Kenji received a suspicious e-mail from a math quiz and couldn't help but stay curious to answer it overnight. But he didn't know it would cause a catastrophe.
A mysterious avatar appeared in the virtual city oz connected to the world. The password of the oz management building, which he thought was perfect, was analyzed and obtained by a group of people led by Kenji through a quiz. Invaded the core management building of oz and seized the accounts of more than 400 million people, causing great chaos in the world. Paralyzes the traffic management system and emergency notification system, creates chaos in police stations, fire stations, and hospitals, causing a massive paralysis. Invading waterway management procedures, submerging the city in water, halting all kinds of financial flows, and throwing the whole of Japan into chaos. A Rong's mother-in-law, who caused an uproar, showed her kingly demeanor in front of Zhang Huang's bewildered people. Use the prestige of the elders as a weapon to lead the battle. Play against virtual opponents in simulated connections. However, the personal display that seized the account in OZ with a simulated image was a fake personal display, and the real Kenji was also arrested for this reason. In OZ, there is a group that summarizes various fighting skills. In the area under his management, according to certain rules, various fighting competitions are held. But that virtual opponent revoked his administrative rights, turning the entire oz world into a fighting arena. That is to say, this virtual adversary controls countless accounts and begins to attack the real world.
