(傷物語) Translated as "Damaged Goods Story". Prequel to Bakemonogatari, centering on the spring break when Araragi Koyomi turned into a vampire and how he solved his problem with the help of Oshino Meme.
Before being published as a light novel, the story was first released in the first volume of the literary magazine Pandora under the title "Koyomi Vamp" (こよみヴァンプ).
This tag implicates monogatari_(series) (learn more).