Reito Mizuhara, a young researcher diagnosed with multiple sclerosis, is put into cryosleep while a cure for his condition is sought. Before going under, he confesses his long-held feelings to his childhood crush, Erisa Tachibana, who promises to wait for him. Five years later, Reito awakens to a shocking reality: 99.9% of the male population has been wiped out by the “Man-Killer Virus,” leaving him one of the few immune survivors. Now, as one of only five remaining men, Reito is seen as a crucial asset for humanity’s survival and is expected to father as many children as possible.

Despite the immense pressure and temptations surrounding him, Reito is resolute in his loyalty to Erisa and refuses to be with any other women. As he navigates a world where society’s survival hinges on him and the remaining men, Reito’s journey becomes one of resisting desire, searching for his true love, and uncovering the mysteries behind the virus.