Kamaji is an old man with six arms, who operates the boiler room of the Bathhouse. These arms can apparently extend indefinitely, so as to allow him access to the upper cabinets from his original position. A number of Susuwatari (ススワタリ) work for him by carrying coal into his furnace. He has a large cabinet where he keeps all the herbs that are used in the baths, which he crushes with a Yagen.
After some persuasion, he allows Chihiro to work at the bathhouse and even pretends to be her grandfather to protect her, though this ruse does not stand for long. He later takes an injured Haku into his boiler room and cares for him while Chihiro, given train tickets by Kamajii, journeys to Zeniba's cottage. At first he seems cold and uncaring, but by the end of the film he seems to have grown a soft spot for Chihiro and for anyone whom she calls her friend.