Humanity crumbles as monstrous creatures known as Grenimals emerge, born from corrupted desire and preying on a terrified populace. Among these horrors are the Lycanthropes, savage beasts that revel in chaos, and the Vampires, who view humans as nothing more than cattle to be drained. The world teeters on the brink of madness, and rising to face this encroaching darkness are the Executioners, warriors who hunt what should not exist. The story centers on Mutuki, a stoic and battle-hardened fighter, and his sharp-witted partner Yuri, as together they plunge into one supernatural mystery after another. Each case unveils horrors festering in the shadows of their crumbling world, where the line between hunter and hunted is destined to shatter and survival demands cruelty.

The series is set in a dark fantasy world rotting from within, besieged by Grenimals. The protagonists belong to the Executioners, an organization or group that confronts these beings. Yuri often serves as the perceptive strategist to Mutukis front-line combat prowess. The narrative follows an episodic structure where the pair investigates cursed incidents, though an overarching plot develops regarding the origins of the Grenimals and the true cost of being an Executioner.