Anime Angel72's fanfiction crossover between Rosario + Vampire and Ao no Exorcist. Contains a female Rin.
Yuri gives birth to twins who she names Rin and Yukio. Shiro arrives and decides to take care of Yukio while Mephisto decides to get rid of the Rin who was born with the blue flames. He abandons Rin in the woods only to be found by Akua Shuzen. Akua decides to raise Rin in the monster world. 15 years later Rin a skilled fighter goes to True Cross Academy. She meets her long lost twin Yukio who does not know she is his twin sister.
Rin Shuzen- The adopted daughter of Akua Shuzen. She is a very skilled fighter with a demon sword. Her mother has trained her in Hōgetsu Jigen-Tō (lit. Moon-Crushing Dimensional Sword). Similar to her Aunt Moka she wears a Rosario to seal away her blue flames thought she does not have an outer personality. Rin is usually very calm and collected until she is pushed over the edge. Unlike Yukio Rin is Half-demon and half-vampiress. This is because Akua injected her with her own blood to save Rin's life.