Due to a shortage of ambassadors for the newly conquered worlds left behind by the Bebaus brothers' rapidly advancing fleet, Lafiel is appointed Territorial Ambassador of the planet Lobnas II. Upon arrival on the planet Jinto, Lafiel discovers that the planet has been used as a prison planet by the United Mankind, with a million prisoners on the planet's only inhabited island. The inmates are divided into three groups. The western section houses women, the eastern section houses males, and the central section is mixed on the condition that all inmates staying there are sterilized. Women in the western sector desire to leave the world of fear for men, but when they do, men in the east rebel and overthrow them.