During Golden Week before the events of Bakemonogatari, Koyomi Araragi discovers that his classmate Tsubasa Hanekawa is hiding an abusive home life behind her perfect-student composure. The stress awakens a cat aberration called Black Hanekawa, which possesses Tsubasa and begins attacking people at night. Araragi, still adjusting to his own recent encounter with a vampire, turns to the eccentric Meme Oshino for help subduing the apparition without harming its host.