Koume is a kokeshi doll Engimon residing in the Amanogawa children's room, one of five guardian creatures alongside Haruo the papier-mâché dog, Kin-chan the goldfish paper balloon, Hebikura the bamboo snake, and Chief Daruma the daruma doll. These guardians quietly watch over siblings Yamato and Himi.

When a mysterious beckoning cat lures Himi away and vanishes, Koume and the other Engimon unexpectedly spring to life. Their sudden animation astonishes Yamato, who joins their quest to find his missing sister. Koume participates in this group mission to locate and rescue Himi.