Nanba Prison is the largest prison in Japan. It is built on an isolated island and is incarcerated with extremely vicious and dangerous prisoners. In the long history of this prison, no prisoner has been able to overcome the thick walls and escape successfully. Shuang Liuyi (voiced by Guan Zhiyi) is the chief guard of the 13th prison. He is known as the No. 1 of Nanba Prison. He is not only very serious about his work, but also wants to do his best in his hobbies. There are four prisoners in the 13th prison - Jyugo (voiced by Uemura Yuxiang), a teenager with a dark past who wants to escape from prison, Uno (voiced by Kakihara Tetsuya), who is a playboy who accepts women as long as they come, Niko (voiced by Kobayashi Daiki), who is an American but is extremely crazy about Japanese anime, and Rock (voiced by Shiozaki Ailu), who thinks the two most important things in life are eating and sleeping. Shuang Liuyi, who has always been confident in his abilities, found that he had no way to deal with these four people who did not play by the rules.