In the 1860s, Japan is in turmoil. Enter the strange and disturbing world of Japanese yokai author Natsuhiko Kyogoku in Requiem from the Darkness, an animé series based on Kyogoku's tales of supernatural folklore. Going back to the 19th century, we view this world from the perspective of Momosuke, a writer of children's riddles who is looking to branch out and write an anthology of 100 supernatural stories. While collecting material for his book, he happens across a trio of strange characters who always seem to be somehow involved in all of the local myths and legends: Mataichi, the diminuitive leader of the group, who sells charms and spells; Nagamimi, a mystic master of disguise; and Ogin, the manipulative puppet-mistress.
Momosuke soon discovers that the trio is, like him, traveling around the country searching for supernatural legends. Their job, however, is to mete out karmic justice to any evildoers who have been using the legends for their own personal gain. Since Momosuke's destinations are often the same as theirs, they continually bump into one another. Momosuke not only gets a chance to build up his story collection, he begins to learn more and more about what the trio are really doing through witnessing their unorthodox interpretations of "justice".
Tired of writing riddles for children, Yamaoka Momosuke plans on gathering spooky and gruesome stories and publishing them in an anthology called Hyakumonogatari ("One Hundred Tales"). While researching these old myths and legends he comes across a mysterious trio who call themselves the Ongyou. They are detectives who are investigating the legends to reveal their truths...and bring those in the wrong to justice. Each time Momosuke meets the Ongyou he must face horrible truths and battle with his morals, but he's seeing things he shouldn't be seeing...