The boy Yoshiro Kizuki lives an ordinary life Like any 16-year-old high school student.But one day, his life turns upside down, and he discovers that there is a being,An alien who came from another dimension called Hosha and began to live inside him, and he is an Exophile. Yoshiro and Hosha build a strong friendship, as, with the help of other people, they fight the group of Exophiles who secretly came to Earth after Hosha, in the aim of protecting the population and revealing the grand plan that the Exophil Empire is preparing to envade the planet of the second demention: the earth.