Kapaeru is a kappa demon serving on the Yokai Patrol team tasked to capture escaped demons. He operates primarily in the human world as an information gatherer, often deceiving humans into believing his distinct kappa appearance is merely a disguise. His duties involve tracking demonic activity and reporting back.

His character portrayal varies significantly across media. In the OVA, he maintains a close relationship with a secret human contact aiding his clue-gathering; both meet their end at the hands of a demon possessing Yukihime. Within the manga continuity, he betrays Enma and Yukihime, actively opposing them.

A long-term resident of the human realm, Kapaeru leverages this familiarity to locate targets. He exhibits typical kappa traits, including water-based abilities and occasional comic relief. Physical characteristics feature rosy cheeks and his distinct kappa form, sometimes mistaken for a frog. His role shifts from supportive teammate in some narratives to antagonist in others, notably the manga where his betrayal drives the plot.

His abilities encompass spraying water and utilizing his aquatic nature for reconnaissance. Loyalty appears specific to individuals in certain storylines, while self-serving motives drive him in others. His narrative function alternates between providing tactical support through intelligence gathering and creating conflict via treachery. Relationships range from cooperative to adversarial, impacting group dynamics and mission outcomes.

Kapaeru's storylines frequently involve investigations into demonic possessions and supernatural disturbances. His knowledge of the human world proves valuable for navigating urban environments and identifying concealed threats. His development focuses on immediate mission objectives.