Yotsugi Ononoki is an expressionless human corpse tsukumogami and the shikigami familiar of Yozuru Kagenui. 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 originally introduced as an antagonist, she eventually becomes a frequent supporting character. Later in the series, she pretends to be Tsukihi Araragi's doll and lives in the Araragi household in order to protect Koyomi Araragi. She is the narrator of an arc in Orokamonogatari and the titular protagonist of three main arcs: Yotsugi Doll, Yotsugi Buddy, and Yotsugi Shadow, and of two minor arcs: Yotsugi Future, and Yotsugi Stress. Yotsugi looks like a 12 year old girl with turquoise hair, green eyes, pointy ears, and a strange orange hat with googly eyes. Her outfit consists of a frilly orange dress in varying shades of color, striped blue and grey stockings, and yellow boots. As Tsukihi's doll, she commonly wears a kimono, likely due to Tsukihi dressing her up to match her fashion sense. Possibly due to the circumstances surrounding her creation, Yotsugi is seemingly void of any obvious personality traits. Her facial expression almost never changes from neutral and she speaks in a flat, monotone voice. Throughout the series she explores her identity by adopting various signature phrases and gestures. In her first appearance, she frequently ends statements with "Boku wa kimegao de sou itta", roughly meaning "I said, with a posed look", notably using the masculine "boku wa" to refer to herself. She would later drop this phrase out of embarrassment and regret, indicating her ability to express such emotions in her own way. When Koyomi Araragi mentions the subject he is immediately hushed by her and told never to bring it up again. She retains a mannerism of referring to anyone as an older sibling, even in situations where she's technically older. She refers to Koyomi as "oni no onii-chan", often translated as "devilish big brother" or "devil boy," referencing his relation to vampires since they're commonly considered to be demons. She has been shown to address Deishuu Kaiki as Kaiki-onii-chan as well, greeting him with a peace sign hand gesture and the words "yay" and "peace", much to his annoyance. She seems to keep the "yay peace peace" mannerism from then on. Kagenui is the only person she calls her big sister without using it as an honorific (i.e. only Onee-chan as opposed to Yozuru-Onee-chan.) Kagenui has admitted there is some significance to this after Koyomi notices, but never explains what it is. Despite appearing almost entirely stoic, she still has hinted at feeling genuine emotion. She's mentioned how she considers Koyomi her friend on multiple occasions, such as when giving him advice "as a friend" as opposed to as an oddity specialist. She's also expressed how she wouldn't want to have to harm him despite needing to follow orders as a shikigami. Yotsugi also has an appreciation for muscles.