Kannazuki No Miko

Two high school students at the elite Ototachibana Academy in the made-up Japanese town of Mahoroba are Himeko Kurusugawa and Chikane Himemiya. They are also the solar and lunar mikos' reincarnations. The sisters' long-sealed personalities awaken to defend the planet when their ancient foe, the Orochi (the eight-headed Yamata no Orochi of Japanese folklore), emerges once more. On October first, Himeko and Chikane's joint birthday, the Orochi awakens (Kannazuki, "the godless month," in the conventional Japanese lunar calendar). Sma Gami, a childhood friend of Himeko's, is the first Orochi to attempt to kill one of the mikos (who is in love with her). But when a bright burst of light awakens him, he refuses his fate and swears to protect Himeko from the other Orochi. While Sma thwarts the Orochi's attempts to murder them, the mikos must awaken Ame no Murakumo in order to battle the menace.