After growing weary of writing riddles for children, Yamaoka Momosuke decides to collect eerie and gruesome tales for an anthology titled Hyakumonogatari, meaning “One Hundred Tales.” While researching these ancient myths and legends, he encounters a mysterious trio who call themselves the Ongyou. These detectives investigate the legends to uncover their truths and to bring those in the wrong to justice. Each time Momosuke confronts the Ongyou, he must face grim realities and wrestle with his own morals, all while seeing things he should not.