Yukito Ayatsuji (born 1960) is a Japanese writer of mystery and horror novels. He started writing as a member of the Kyoto University Mystery Club, a society dedicated to the writing of fair play mysteries inspired by the Golden Age greats. The Decagon House Murders was Ayatsuji’s debut and is considered a landmark crime novel in Japan, where it revived the traditional puzzle mystery format and inspired a new generation of writers. The Water Mill House Murders is the sequel, again starring the great detective Kiyoshi Shimada.