 In the train on the way there, Kei has a mysterious dream of a huge tree and a woman who seems to be lost in sadness.In Hemizuka, Kei learns the secret concealed in her own blood through various meeting with an Oni Slayer, a friend of her late mother, a young girl accompanied by a white fox, and even the mysterious girl from her dreams.Throughout the story Kei is antagonized by the twin oni Nozomi and Mikage.