After the Bebaus brothers' fleet conquers various worlds, Lafiel is tasked with becoming the Territorial Ambassador of Lobnas II due to a shortage of ambassadors. Upon reaching the planet, Lafiel and Jinto uncover its dark history as a prison planet used by the United Mankind, with a million inmates segregated into women-only, men-only, and mixed sectors where sterilization is mandatory. The women in the western sector aim to flee due to fear of the men, triggering a rebellion in the male sector led by Jinto to prevent their departure. Simultaneously, an enemy fleet approaches, forcing Lafiel to evacuate Jinto in haste.