In a post-apocalyptic Japan, a mysterious alien spore from space infects the northern half of the country, turning its inhabitants into ravenous, antler-sprouting zombies. A governmental quarantine zone is established, effectively splitting Japan into two territories: the zombie-infested North and the human-occupied South. Kika, a young girl, awakens to discover that her mother, Rikka, is the sinister queen of the zombies. Rikka and Kika's uncle, Yasushi, harbors deep resentment and hatred, driving the family's involvement in the dystopian conflict. Kika sets out on a perilous mission to put an end to her mother's reign of terror and restore peace to the divided nation.

Amidst the chaos, Kika teams up with a ragtag group of survivors, each possessing unique skills crucial for their survival against the relentless undead horde. Armed with a chainsaw katana powered by her prosthetic heart, Kika battles through throngs of zombies to reach her mother's stronghold. As Kika and her companions face grotesque mutant zombies, hostile human factions, and the ever-present threat of infection, they uncover dark secrets about the origins of the outbreak and the true extent of Rikka's power. The journey challenges their resolve, loyalty, and humanity, pushing them to their physical and emotional limits as they fight for the future of their country and the survival of mankind.