Hayou no Tsurugi: Shikkoku no Mashou

A girl named Rasutel-nicknamed Rasu-lives in the Floating Castle, where she fights demonic creatures. Chosen by the rebellious spirit of the Demon-Breaker sword, she sets out on a mission to rescue a princess kidnapped by a Youki. Along the way, she gets help from an unusual Youki named Anshu, who lacks the typical colors of his kind. But her journey is complicated by her younger brother, a demon-being who hunts her for her golden eyes-a legacy of their father, the Golden Youshu.