It is 1599, one year after Toyotomi Hideyoshi's death, and the human world is sliding back toward war. Yase-hime, head of the ten oni clans, is worried for her people. She visits each clan — now scattered across the land — and asks them all to withdraw from human contact. On the night they obey and gather together at Yase village, she is kidnapped and put into a deep sleep by an unknown enemy. Suzumori Yukina is the head of her household and was Yase-hime's ninja guardian. She now faces a question Yase-hime had specifically asked her not to face: whether to enter the human world and search for a cure, or to honor the request and do nothing.