Gedoumaru (外道丸) is a Shikigami of the Ketsuno Clan. She was given to Sakata Gintoki of the Yorozuya as a precaution, during the Exorcist Chapter, by Ketsuno Ana, who had requested the Yorozuya's assistance.
She has straight, black hair and dark red eyes. On the top of her head, she has two small, yellow horns. Her usual attire consists of a black robe. She wields a giant, fortified club which she carries with ease.
Despite her innocent and cute looks, she is extremely strong. Gedoumaru will do anything to beat her opponent, as seen in Episode 195 when she tricked the other Shikigami into thinking her mother had just died, when it was all just an act to get them to lower their guard. If her master shows any sign of weaknesses, she will turn on him. She is loyal only to Ketsuno Christel.
Gedomaru was caught by the Ketsuno clan when she was tearing up Mt. Oe during the Heian period, and was forced to serve them ever since, as told by Gedomaru herself in Episode 195. Ketsuno Christel was the only one who considered her as a friend.