In a world where humans have been nearly wiped out, zombie society faces a severe food crisis. Zombies must consume human flesh to maintain their intelligence and civilization, but the dwindling human population threatens their very existence. Wataru is a rare zombie who retained his full human intellect and emotions after turning. Unlike the mindless horde, he can think, plan, and feel guilt. To solve the food shortage, he conceives a forbidden scheme: locate the few surviving human men and women, force them to breed, and farm humanity as livestock.

Wataru's first breakthrough comes when he tracks down a living woman. She is Yuka Tachibana, his ex-girlfriend from his human life, and he still carries feelings for her. This personal connection immediately complicates his coldly rational plan. He brings Yuka to a middle-aged recluse named Katsu, a crude, sexually frustrated man who serves as the designated male for the breeding program. Wataru locks them together, overriding his own emotions for the sake of the plan. Yuka feels deeply betrayed. After a series of violent encounters with other survivor groups, including a charismatic leader named Yuuki, Yuka becomes pregnant not by Katsu but by Yuuki. Wataru eventually kills Yuuki and takes the newborn girl, naming her Umi, to raise her himself.

Years pass. Wataru raises Umi as his own daughter, though she was always intended as a tool for the breeding program. Umi grows into a beautiful young woman with no knowledge of the world before the zombie apocalypse. When she reaches puberty, Wataru forces her to mate with Katsu. Despite the horrifying circumstances, Umi and Katsu develop a genuine emotional bond. Umi gives birth to twin boys, Shuu and Kou. Wataru struggles with conflicting feelings: he loves Umi as a daughter, yet he also views her newborn grandchildren as food, fighting the urge to eat them. Katsu eventually sacrifices himself to save the family from a zombie horde, leaving Wataru as the sole adult guardian.

Years later, Shuu and Kou have grown into teenagers. With Katsu dead, the only male capable of continuing the breeding program is Wataru himself, but he is a zombie. He decides the boys must find new human women to mate with. Shuu, curious and eager about sex, agrees to join Wataru on a journey to search for survivors. Kou reluctantly follows. After a long and dangerous trek, they reach Himeji Castle, where they discover a woman named Fūko and her daughter Sakura. Fūko initially attacks them but relents when she learns Wataru is a half-zombie. She reveals she has a sick daughter named Mizuki who is turning into a zombie, and she desperately needs Wataru's help. Fūko has been researching a vaccine against the zombie virus for sixteen years, ever since her father, a scientist, first created a flawed cure that caused an outbreak within their own family. The story delves into the past, revealing the origin of the pandemic and the mystery of a chained girl in the castle tower. As Wataru and his group navigate this new environment, the narrative shifts from pure survival horror toward a broader exploration of civilization, ethics, and the possibility of reversing the apocalypse.