The Cursed Priestess

When a mysterious girl proclaims herself to be the Priestess of the Dragon God, Akane and Tenma investigate and learn that the girl is Tenma's younger sister, Ran. However, Ran does not recognize Tenma as her brother and has apparently joined the Oni Clan. When Akane awakens from a nightmare and finds dead butterflies under her quilt, Yasuaki reveals that she is cursed and will die the following night.