There is a certain insect that exists. It is a human parasite. As it develops, the larva continues to grow, and the host will eventually die. There is no cure. Two children, Tetsuro and his sister Nana, lose their mother to this parasite and move with their father to Yamejima. On the island, it seems that Nana has become infected, and Tetsuro loses hope. But suddenly, a mysterious islander confronts him...