Based on the erotic game by Active.

Bible Black Only explores the sexual misadventures of the supporting cast from the main Bible Black series. Miss Takashiro reminisces on her demonic capture, Itoh reveals her sadistic side, and Saeki is stalked by her classmates. Bible Black Only is a series of stand-alone episodes that do not affect the continuity of the main Bible Black series, and it contains footage that was previously only available on the R2 Bible Black Perfect Collection DVD.

(Source: Anime News Network)