Shinobu is a girl who lives with Meme in the abandoned building. She appears to be an eight-year-old girl, but she was originally a beautiful vampire (the vampire that bit Koyomi, thus turning him into a vampire as well) who had lived for more than 500 years. After the events at the end of Koyomi Vamp, she was left in a weakened condition with no powers or traces of her original personality, and therefore had to abandon her "Kiss-shot Acerola-orion Heart-under-blade" (キスショット・アセロラオリオン・ハートアンダーブレード?) name. She was named Shinobu by Meme at the beginning of Hitagi Crab, suggesting her kanji name Shinobu (忍), having "heart" (心) under "blade" (刃), matches with her original personality (but in typical Nisio Isin playing with kanji, the しのぶ pronunciation of the kanji 忍 means "fern"). She doesn't openly talk to anyone until "Karen Bee." Ever since "Tsubasa Cat" where she starts living in Araragi's shadow, she no longer needs to suck his blood on a regular basis in order to stay alive. She forms a physical connection with Araragi where they can feel each other's emotions and senses.
In Mayoi Jiangshi, in the alternate timeline, Shinobu went berserk when Koyomi was killed by Black Hanekawa so she swore to destroy the world and created the Jiangshi that has been swarming the town. It seems that she truly cares about Koyomi and when she saw Koyomi was alive in the alternate timeline, she started weeping blood. Koyomi states that he will die with Shinobu when the day comes. It seems that she does not like Nadeko very much. In "Shinobu Time", a mysterious entity seems to be after her and she told Koyomi that she had encountered and fought this entity before in her past but failed.
