Kapa is a recurring minor spirit with a green body, a white disc on his head, and a duck-like beak. He wears a turtle-like shell on his back. Kind and grateful, especially toward Takashi Natsume who saved him twice from dehydration, Kapa expresses his gratitude by sharing freshly caught fish and actively seeking chances to assist Natsume. He demonstrates loyalty and willingness to help those kind to him. Within the plot, Kapa primarily appears weakened by dehydration, needing water to recover. His significant contribution comes when he warns Natsume about an evil exorcist draining spirits' blood, acting as an informant. During this encounter, he acknowledges Natsume's capabilities and connections to powerful spirits like Misuzu and Benio. Kapa is a member of The Dog's Circle. His name does not appear in the Yuujinchou, and while he likely possesses a true name, it remains unknown. This character subverts traditional Japanese folklore depictions of kappa as mischievous or malevolent, instead portrayed as helpful and benevolent in his interactions with Natsume.