Orphan girl Mei is adopted by a wealthy family and receives the ticket out of the orphanage. The girl finds herself with a sister who has arrived at the family under similar circumstances. They bond and become close. Things take a turn for the worse, however, when the family's fortunes take a nosedive allowing the family to keep no more than one of the girls. That means someone has to trod back to the orphanage. Well, neither is volunteering.

Black Maiden: Chapter A

Mei lives in an orphanage, but she is adopted by the wealthy and kind Uda family. The family already has an adopted daughter Rana. While Rana seems weird, Mei and Rana find that they have a lot in common and become like real sisters. The girls then learn that the Uda family's business has collapsed and they can only keep one of the daughters. One of the girls will be returned to the orphanage in a week. Revenge is soon planned.

Black Maiden: Chapter Q

Kamata Maro (Tsukamoto Takashi), a freelancer who calls himself a detective, works part-time at a yakiniku restaurant in Kyoto, while living a carefree life. He spends his free time with Gennosuke (Daichi Asai), a bumbling fighter, and Kenta (Yuta Yamazaki), a genius hacker. One day, he receives a request from his favourite cabaret girl to search for his missing father.