Wandering exorcist Kusuriuri books passage on a luxury ship bound through what sailors call the Dragon's Triangle, sharing the voyage with the boastful merchant who owns it, a young samurai carrying a famous sword, a Buddhist monk, a travelling minstrel versed in ayakashi lore, and a servant girl named Kayo. When the ship is steered off course into cursed waters, Kusuriuri senses a mononoke stalking the passengers and sets about working out its Form, Truth, and Reason before it can take them.