In 2007, popular mystery author Kyōgoku Natsuhiko attempted to adapt a collection of random stories known as the Mimi bukuro or Tales Heard into kaidan, tales of the strange and mysterious for today’s readership. The writing experiment ended with Kyōgoku questioning his own writing abilities and publishing his small collection of adapted stories into a book that was not considered very frightening. Although the experiment failed, Kyōgoku’s efforts raise the question, “if not kaidan, what is frightening in the twentieth century?” The reason why kaidan are no longer frightening is because their central characters, yōkai, have been displaced from the horror genre. Today the yōkai that were once popular in the Edo period have been “cutesified” for businesses, films, and children’s shows. What is frightening today is no longer the Edo period monster, but rather aliens, ghosts, scientific monsters, and serial killers that represent a fear of the unknown. While the unknown has been a fear of man since the beginning, how it is symbolized and interpreted changes over time based on society and individual experiences. Chapter one traces the development of yōkai’s transformation from traditional horror story icons to children’s characters and role models. Chapter two analyzes and compares four of the original stories from the Mimi bukuro to Kyōgoku’s adaptation to understand what was scary during the Edo period, and what Kyōgoku deemed frightening in modern times. Chapter three analyzes three different monsters and explains why they were frightening and what problems or unknown situations each monster represented for modern audiences.