Tradition / Region: Japanese Mythology
Alternative names: Kiukan
Category: Cow
The Myth
Gyūkan is a strange disease-causing entity believed to develop inside the human body. It is depicted as a cow with black horns and was understood as a mass that forms within the lungs.
According to the Shinmonsho, when the Gyūkan develops, it causes severe illness. When the afflicted person attempts to eat, the condition can trigger a sudden seizure and loss of consciousness.
The Gyūkan was considered difficult to treat once it had fully developed, although the Shinmonsho describes various acupuncture treatments that could be used against it. The creature is illustrated alongside other disease-causing beings in the sixteenth-century medical manual.
Sources
Takahashi, Toshihiro. “牛癇 (Gyūkan).” 新版TYZ 妖怪図鑑 (New TYZ Yokai Encyclopedia). June 27, 2021. Accessed August 16, 2026. https://tyz-yokai.blog.jp/archives/1078437904.html