KOYUKI is cosplaying as Shinobu Oshino from Bakemonogatari. Bakemonogatari is a Japanese light novel series written by Japanese novelist Nisio Isin and illustrated by Taiwanese illustrator Vofan; the series is published by Kodansha under the Kodansha Box imprint. The story centers on Koyomi Araragi, a third year high school student who has recently survived a vampire attack, and finds himself mixed up with all kinds of apparitions; gods, ghosts, mythological beasts, and spirits. An anime adaptation by Shaft started airing on July 3, 2009 and went through a total of 15 episodes. The prequel novel, Kizumonogatari was recently announced as being green-lit for anime production.
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 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" name. She was named Shinobu by Meme at the beginning of Hitagi Crab, suggesting her kanji name Shinobu , having "heart" under "blade" , matches with her original personality. 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 others emotions and senses. Koyomi states that he will die with Shinobu when the day comes. Her next story was revealed to be Shinobu Time.