Veteran adventurer Hakura, a seasoned monster hunter, barely survives a deadly encounter with a hydra. In his dying moments, he is rescued by Leen, a mysterious young woman who possesses the rare and formidable ability to tame any monster without effort. Leen, a descendant of the legendary primordial witch Ringleen, has little understanding or attachment to human emotions, viewing people as puzzling creatures. Grateful for his life, Hakura offers to become her bodyguard, and the two set off on a journey across a world where humans and monsters coexist uneasily. Despite their partnership, they constantly clash: Leen’s blunt, self-assured, and sometimes reckless approach to monster-taming runs against Hakura’s practical, cautious adventurer’s instincts. Their travels take them through varied regions where they take on dangerous cases involving creatures that are rarely what they seem. Rather than simply slaying monsters, Leen must understand their behaviors, ecosystems, and personal histories to resolve conflicts. Accompanying them is Ao, a sentient blue slime who acts as a veteran companion and provides a measured perspective on their misadventures. As the unlikely trio navigates encounters with hostile hydras, territorial beasts, witch hunters, and ancient secrets tied to Leen’s lineage, their arguments give way to an evolving bond. The narrative explores themes of coexistence, prejudice, and the blurred line between human and monster, all set against a backdrop of sprawling fantasy landscapes and episodic monster-themed mysteries.