According to a game by Mink's M no Violet division.

When it comes to preceding OVAs from Night Shift Nurses, the plot of the one centers around Yagami Yuu who likes being a responsible nurse at a hospital, she tooks her work on the first page, giving pleasure on the hopeless patients in a descending spiral in a non-stop way, each time more perverted and dirty, reaching the downs of sexual behavior.