Because of an enigmatic illness, the prodigy Iria Akagami has been compelled by her relatives to remain in a manor on the secluded Wet Crow's Feather Isle, surrounded by misty cliffs, accompanied only by a few housekeepers. To stave off boredom, Iria welcomes an array of other brilliant minds to her residence: the computer prodigy Tomo Kunagisa and his unnamed aide, the adept diviner Maki Himena, celebrated painter Kanami Ibuki, scholarly researcher Akane Sonoyama, and acclaimed chef Yayoi Sashirono. The gatherings proceed normally until one night a guest is discovered brutally slain under a moonless sky, leaving no trace of the assailant or motive. Suspicion swells among island inhabitants as the murderer stays free, prompting Tomo's aide to take it upon himself to identify the killer before any additional tragedies unfold while the rest of the guests remain unaware.
