Yumiko Sato was spirited away by yokai when she was seven-years-old. Kagami, the yokai lord of a magical realm that exists beyond mirrors, allowed her to leave, but vowed that he would come for her when she turned eighteen, whereupon he would consume her, body and soul. When she returned from that strange world, Yumiko found that everything had changed. She could see the supernatural monsters of Japan called yokai, when no one else could. She could return to that terrible place by walking through mirrors. And her mother had disappeared. With less than a year left before Kagami comes for her, Yumiko has become an expert at hunting down and dispatching yokai with her mirror sword, sending them into the mirror world, where they can no longer harm anyone. She prepares for the battle of her life and hopes that when the yokai lord comes for her, she will be strong enough to defeat him, saving not only herself, but her mother as well. Between the ghosts, demons and urban legends that find their way into her life, Yumiko has little time for people. So when things go south, she finds herself in an uncomfortable position, working alongside a ragtag group of humans and yokai to try to save the world before evil forces march upon it. Things are not what they seem, and Yumiko has just scratched the surface of the mysteries surrounding yokai, and just who she has become since returning from that fateful trip to the yokai realm.