Gedoumaru 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 and cruel. 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 Ana. She also seems to respect Sakata Gintoki to some extent.
Sakata Gintoki : From a rough start to a respected comrade, Gedoumaru threatened Gin on how she dislikes weak masters. Overtime Gedoumaru develops trust and respect for Gin. She also admires how Gin does not fear demons in episode 249.
Combat: She has shown to have quite well combat skills. In episode 195 she wipes out 4 surrounding shikigamis that are 10 times her size and in episode 249, she wipes out many demons/shikigami who have surrounded her in an instant.
StoryGedomaru 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 Ana was the only one who considered her as a friend. Ketsuno Ana. Gin got her a present but the demons refused to serve humans and surrounded the odd jobs crew. Gedoumaru slaughtered many of them in an instant. She then took Gins advise to buy something for herself.
Gedoumaru goes back to help the Yorozuya alongside with Ketsuno Ana, Ketsuno Seimei, Shirino Douman and other diviners. Gedoumaru leads the Shikigami troop to fight the Amanto while the diviners scare them away using illusions.
After the first encounter, Gedoumaru helps Otae to take care of the injured people as well as bringing in nutritious food (Pandemonium) to those in need.