A sudden disaster plunges Japan into chaos, transforming the populace into ravenous zombie-like creatures. In the wake of this catastrophe, middle school student Tsuranuki Tsutsuki becomes separated from his family and witnesses his twin sister kidnapped by the undead. Armed with a gun and skills from a uniquely strict upbringing, Tsuranuki ventures into the monster-infested ruins of Tokyo to find her.

His search leads him to a chance encounter with a mysterious high school girl named Karina Karina, who wields a powerful katana known as the Corpse Blade. Karina reveals that she comes from an ancient line of zombie hunters called Corpse Blades and claims that Tsuranukis father requested her protection for him and his sister. Together, this unlikely pair forms an alliance; Tsuranuki provides ranged cover with his firearm while Karina engages the hordes in close combat with her supernatural sword.

As they journey through the desolate streets, they discover that the zombie threat is more complex than it initially appeared. The infected are not a uniform mass but include mutated creatures with unique abilities and a hidden hierarchy. Among these are the Corpse Puppeteers, special zombies created by mages with the power to generate and control other undead. This layered ecosystem of monsters forces the pair to confront not only waves of standard zombies but also powerful, intelligent elite creatures.

The narrative arc follows Tsuranukis desperate rescue mission, which quickly expands into a larger exposure to a hidden supernatural world. For Karina, the journey is one of duty and the revelation of her familys legacy as protectors against these outbreaks. The series builds toward confrontations with the higher-ranking zombies, exploring the origin of the disaster and the true nature of the Corpse Blades power. The storyline concludes with an abrupt resolution, wrapping up the immediate threat in a concise, three-volume run.