One night, while taking out the trash, Kazuki Itou encounters a disheveled girl dressed in gothic lolita attire. As he walks past, she asks, "Would you have a little sister?" to which Kazuki confirms that he does. Following several further encounters with this peculiar girl, he discovers that she has gained entry to his apartment and is stalking him, determined to actually become his younger sister. What does this imply for Kazuki's actual sister, Hikari? If the local urban legend regarding the demon lolita holds true, she will kill Hikari and assume her place. However, it may prove that Hikari's alleged fate is preferable to what the lolita has planned for Kazuki.