A medical student named Reito Mizuhara from the National Advanced Medical School in Tokyo is afflicted with a rare cellular sclerosis. To rescue him, he is subjected to cryogenic sleep for five years. When he finally wakes up from the slumber, he realizes that the world has been decimated by a pandemic produced by the Male Killer (MK) virus. The virus has wiped out all males worldwide, except for Reito and four other people. They, too, were in cryosleep during the outbreak. Reito and his fellow survivors are Earth's only chance for survival. They have the responsibility of producing children with as many women as possible to ensure the planet's continuity. However, Reito is determined to locate his childhood friend and love interest, Elisa Tachibana, who vanished three years ago. Despite his companions' concentration on procreation, Reito resolves to pursue his quest for Elisa while also exploring the virus that nearly destroyed all of humanity.