The world is a perilous place. Humans and demons coexist under fragile conditions, governed by an unspoken pledge not to interfere with one another. Unfortunately, there are always those willing to break the agreement for their own selfish gain. Seeking to combat these outliers, the Japanese government employs the Taimanin—an elite group of female human ninjas—to maintain the balance of power between the mundane and the otherworldly. After the defeat of her greatest nemesis Oboro, Asagi Igawa decides to retire from the Taimanin and devote herself to a peaceful, average life with her boyfriend Sawaki Kyousuke. However, little does she know that Oboro managed to survive thanks to a pact with a demon. Having sworn revenge on Asagi, she abducts her—along with Sawaki and her younger sister Sakura—and subjects them to sexual and psychological abuse without mercy. Though Asagi's resolution is absolute, there is little she can do when Oboro turns the ninja's closest ones against her by humiliating them in the most heinous ways imaginable.