On a mysterious night, terrible spores suddenly descended on the earth. They penetrated into the human body, took it for themselves, and targeted humans for hunting and eating. High school student Izumi Shinichi (Shota Sometani) was almost controlled by the spores. As a result, the parasitic beast "Xiaoyou" (Abe Takashi) in his right hand started a wonderful coexistence with it. One day, a new teacher Tamiya Ryoko (Fukatsu Eri) came to the school, and she and Xiaoyou were keenly aware of each other's existence. Tamiya introduced A (Ikeuchi Mansaku) and Shimada Hideo (Toide Masada) to Xiaoyou, and invited him to join a network composed entirely of parasitic beasts for development. During this period, Shinichi and Xiaoyou were ambushed by A, and their dependent mother (Yu Kimiko) accidentally became a captive of the parasitic beast. In order to protect the most important people, Shinichi had to attack the vicious parasitic beast... This film is adapted from the comic of the same name by Iwaki Hitoshi.