Kisaki is a 17 year-old high school student who likes her coffee. She lives with her father and brother in a sword shop and loves to hear the story of her ancestor who slew oni during the Age of Warring states in Japan (Sengoku Jidai). Her mother left when she was young and there is a Catholic nun who is like a mother to her. While taking several katana down to the store room she discovers a room that lock has been broken into. Inside she finds a sword which no one has been able to touch for a long time. She is destined to fight oni. For the new era has begun, the time when God will bring about the end of this world.