Jukkakukan no Satsujin (2024)

Six months after Nakamura Seiji, the architect and owner of the Decagonal Building mysteriously died in the main building, seven men and women from the University’s mystery research group visit the uninhabited Tsunojima Island, where the building is located, for a training camp. Around that time, Kawaminami Takaaki, a former club member, receives a letter from the supposedly dead Nakamura, and teams up with Shimada Kiyoshi in order to investigate the truth behind the mystery surrounding Tsunojima.