She is an expressionless human corpse tsukumogami. She's a somewhat unique take on both of the terms that define her, as tsukumogami are normally described as tools or objects that have come to life after years of neglect, and shikigami are typically depicted as being spirits or ghosts that are bound to an onmyouji master. In her case, she's a corpse that was neglected but brought back to life, and a shikigami in the sense that she's a "spirit" that is bound to her master. While rare, she's sometimes referred to as a sort of "zombie." She pretends to be Tsukihi Araragi's doll and lives in the Araragi household in order to protect Koyomi Araragi, often tagging along in his stories. Her physical appearance is 12 years old and her real age is 7 years old, but that doesn't mean that she has the mentality of a child.
