Ukishima Shrine is located in an old, picturesque lakeside town. Shrine maiden Kisaragi Saya lives there along with her father, Tadayoshi. By day, she lives the life of a normal high school student at Sanbara Academy. By night, she hunts the Old Ones. Possessing supernatural physical prowess, the Old Ones prey on humans, and only Saya has the ability to defeat them.