Honoka Asakawa is a reserved university student in wintry Hokkaido. A personal tragedy draws her into experimenting with blood magic — an art thought to have been lost long ago. Through it, she finds herself able to visit a sealed version of Meiji-era Sapporo, where she meets the cheerful and formidable Lady Yasue: a powerful mage who has been trapped in that gilded cage for a full century. As their relationship deepens into something neither expected, the consequences of Honoka's first steps into the hidden world of magic begin to spiral toward a catastrophic conclusion.